Cross-training is the process of training your civilian dwarves in military pursuits, or vice versa, and can offer several benefits. First and most importantly, it can be a good way of raising attributes, leading to stronger, tougher, faster dwarves. Secondly, it provides a handy pool of recruits for when your military takes a beating or gives your civilians a halfway decent chance of defending themselves. Thirdly, it can provide useful replacements for when your legendary mason accidentally blunders into a troll and gets all his limbs broken. Finally, it's a more productive use of time than standing around idling.
There is nothing saying you have to use only one of these ideas; they are all various approaches toward addressing these areas.
 Cross-training (starting a reserves program)
The biggest thing to remember with a reserves program is that if you're going to go, you go all the way. Don't institute something "just for a little while" and come up with a handful of novice reservists; they will not get significant stat increases and you'll only waste time. Time is not something you have a heck of a lot of in a reserves program, typically. Remember that after you draft them, most dwarves are going to need about a year of sparring or training before they're ready for heavy combat. You might not have that much time if you are getting sieges regularly.
 Different Programs:
 Gym (pump operator)
The Gym is the most basic sort of reserves program; it merely consists of building a bunch of screw pumps connected to nothing in a room that's close to food, beds, and drink. After the pumps are built, order them to be pumped manually, then turn on pump operating for your reservists.
- Easy and extremely cheap to set up;
- Requires no continuous oversight on your part.
- Beneficial for fps, air-pumpers consume, produce and move nothing.
- Somewhat fast training; legendary in under a year (if other responsibilities like hauling are minimized).
- Very convenient; gyms can be placed anywhere in your fortress with no issues.
- Inactive marksdwarf squads can operate pumps to cross-train and be activated at a moment's notice - boost attributes without using bolts.
- If desired, you can arrange your pumps so they power one or more indoor waterfalls or other water-powered devices.
- Generates nothing useful other than the increased attributes of the trainee.
- Tons of cancel job spam. Every time a reservist exhausts himself and goes to satisfy his basic needs, you'll see "Urist McScrewpumper cancels Operate Pump: Exhausted."
- If you have any pumps around that actually DO need to be operated every so often (refilling your well, for example), it could be a serious pain to juggle the useless gym pumps and the ones that are actually useful.
 Artillery proving ground (siege operator)
Mass-produce some catapults, line them up near a quarry, and fire away. Works well to dispose of stone from a gulag (see below).
- Trains a skill that's reasonably useful, and provides a place to put all the sub-par siege engine components your siege engineer will doubtlessly create if you're going for superior-quality engines.
- Harasses the wildlife, which is always fun.
- Very slow to train (2+ years for legendary).
- Fairly space-consuming to set up a well-designed and usable proving ground.
- Can be dangerous depending on the biome (especially when elephants are present. If they get winged by a stray boulder, you can bet they're going to be coming straight at you).
- Siege operators are civilians, and will run in fear when an enemy approaches them.
Much like bookkeeping, assign a new dwarf to manager, queue several hundred jobs, and rotate a replacement in as soon as he becomes legendary. For bonus points, queue jobs which need to be repeated anyway, like "Prepare Raw Fish" or "Mill Plants", or jobs for which there is no workshop, like "Make Wooden Bow" or "Make Soap".
- Requires no extra infrastructure at all.
- You need a manager anyway!
- Mostly safe; a manager spends basically all his discretionary time snug in his office, or doing his other assigned jobs.
- Only employs one dwarf at a time; not useful when you have 15-25 candidates for the reserves.
- No announcement when the current intern reaches Legendary status means you can lose time on rotation easily.
- Produces little to no useful attribute gains
The gulag is basically a strip mine that is located far away from your main fortress (so you don't have to worry about accidentally screwing up your own building plans; if you are careful in planning, it may be placed closer to your fortress). Take a big square and start leveling it; it's really no more complicated than that. Since picks can actually be used as weapons, it's worthwhile to give the reservists who will be working in the gulag picks made out of bronze, or, if you are really living large, iron or even steel. Note that you will have to turn your usual mining corps (the civilian miners who are already experienced with mining) off or designate separate mining burrows for this setup to work properly. It might be convenient to use a locked door to isolate the gulag from the main fortress, once a batch of trainees are inside.
- Soldiers can be equipped with picks from the military skill, and use the Miner skill in combat - militia squads of highly-skilled miners can provide a decent defence from early threats
- Toting a pick for close-quarters support might make a legendary marksdwarf more useful, since the pathetic bludgeon damage of his wood and bone crossbows are less important.
- Can be quite useful for producing stones you might not have access to normally, or uncovering veins of precious metals.
- Levels quite fast in sand.
- Relatively little oversight from you.
- An overland hike to the gulag will fight cave adaptation in your military candidates.
- Can easily be transformed into a underground tree farm on suitable maps, providing a safe and replenishable wood source.
- Mining trains all military attributes, so it's perfect for military training too
- Juggling your real miners and your reservists when there's real work to be done on the fort can be a chore.
- Hard to keep dwarves in the gulag for too long; they'll inevitably get hungry, thirsty, and tired and start hiking back to the fortress proper. Could be solved by (temporary) burrow.
- Can be dangerous, depending on the biome.
- Does require some amount of oversight from you, especially when your reservists start getting better at mining and run out of work more quickly.
- Low-skill miners may discover---and then partially destroy---valuable gem or mineral deposits.
- Surplus stone and mining in general are suspected to promote lag.
 Renovation (stone detailing)
Another convenient way to buff up your dwarves, assigning your reservists to mass stone detailing duty increases your fortress' architectural wealth and makes the place look nicer. While they may clutter the halls somewhat, it doesn't require any special allocation of food, beds or drink. Just turn on stone detailing for your reservists and mark up as much of the fortress as you like for renovation.
- Even easier to set up; just assign your dwarves and an area and you're good to go.
- Increases your fortress' value and general happiness.
- Requires no continuous oversight on your part.
- Very safe, if you only assign areas inside the fortress.
- Wealth overflow may bring too many immigrants.
- Serious conflict with engraving assignments; trying to engrave with poorly trained engravers wastes a lot of wealth that essentially comes from nothing. To avoid this, have periods when you only designate stone smoothing, followed by periods where you only designate engraving.
- Careless designation of smoothing areas may have your dwarves trying to smooth walls too close to magma or a river.
Make one or more mason's workshops in an area with a bunch of junk stone you don't care about, or that you're actively looking to clear. Change the workshop settings to allow only your reservists to use it, then tell the workshop to churn out crafts, junk furniture, stone blocks, and trade goods that you can trade en-masse. Alternatively, forbid your reservists from working in your real mason's workshops, order lots of stone constructions built, and pray that your real masons stay too occupied with the workshops to intrude. Works well in conjunction with a gulag. Alternate ideas for sweatshops include a mechanic's workshop, craftsdwarf's workshop, magma kiln, or a magma glass furnace to train mechanic, stonecrafter, potter and glassmaker respectively. Note: Do NOT try this with the carpenter skill unless you have a large supply, or any other resource you don't have in near-limitless abundance. Sweatshops will consume huge amounts of their associated resources, and if you run out mid-way you have probably wasted your time. This includes coke or charcoal used in the normal (non-magma) glass furnace.
- Quantitatively turns a profit. The inferior trade goods can be dumped on the next caravan for more useful commodities like bags, seeds, and logs. Logs are especially useful, since you'll inevitably stamp out lots of bins to support the trade good output.
- Mass-producing blocks makes your constructions higher value.
- Unlike many other training programs, Sweatshops train a skill that is very useful.
- Slow to level.
- Hard to keep the reservists on task, since they'll need to do plenty of hauling to keep their workshop from becoming chokingly cluttered.
- Can be a logistical nightmare; making bins and organizing hauling for the finished goods can be insane if you're working from a gulag.
- Can be dangerous depending on the biome and location of your sweatshops.
- Note also that stone blocks cannot be made into furniture or stone crafts. This may or may not be an issue depending on where you're putting your gulag.
Start off by creating a surplus of longland grass, cave wheat, and/or whip vine and some bags. Create multiple quern all close to the food stockpile which contains the millable plants. Next to this area make a kitchen assigned to an experienced cook. Enable milling for the dwarves you wish to cross-train and order the cook to make lavish meals. As long as your growers provide a steady supply of millable plants and your cook can empty out bags quick enough, the milling jobs will continue.
- Produces a lot of wealth as flour is a high value ingredient
- Produces high amounts of food
- Sustains the training of non cross-training dwarves such as the cook and growers
- Requires a surplus of millable plants to ensure continuous milling, thus you may need to increase the number of plots/growers
- If you don't have enough bags and your cook decides to go on break you may end up having job cancellations for the millers
- Dedicated haulers will be required to keep all workshops clutter free
 Clear Cutting
As long as wood hauling is turned off, dwarves will move from one tree to the next without stopping to bring the wood back. On a heavily forested map, this means that dedicated wood cutters can skill up very quickly.
Of course, this training strategy isn't going endear you with the elves.
- Works quickly
- Trees regrow
- Provides useful lumber to carpenters, charcoal makers, etc
- Can cause problems with elves
- Can cause problems with elves
- Map dependent
- Unless care is taken to only designate a small area for cutting, trainees and haulers can be spread out across the map while, making them vulnerable to creatures and ambushes.
 Dwarf Scouts (ambusher, hunter, marksdwarf)
Marksdwarves are an important part of any military. A bum rush of low level marksdwarves is good, but not as effective as an elite backup squad! Here is what you can do: Draft a comfortable amount of dwarves to hunting, give them all cheap crossbows. Your dwarves should hunt as usual. But you are really training an elite squad of assassins, that will one day hunt goblins instead of groundhogs.
- Easy to start.
- Lots of meat, bones and leather around.
- Aforementioned bones can be recycled to make new bolts.
- Doesn't work on some maps.
- Hunting is dangerous!
- Not as economically productive as some other methods.
 Charm School (Social skills)
(Note: Inspired by milaga's Real Wagon experiment, details of this technique are still being investigated.) This approach is less useful in the new version, as social skills will only produce "Soul" attribute gains. However, teaching your dwarves social skills is useful for training replacement Brokers, and can possibly reduce the chances of tantrums in the fort (more dwarves with high Consoler and Pacifier skill).
Set up a small space with food, booze, and a few beds/chairs/tables, stashing your new immigrants in it, and locking the door for a few seasons. (Be sure to turn off all of their labors and designate it as a meeting place.) With no labors enabled and nothing to do, they'll chat and party and quickly buff up their comedian, flatterer, conversationalist, &c. skills.
- works on any map
- easy to set up
- trains many dwarves at once
- requires almost zero player oversight
- easily scales to any size of immigrant wave
- requires no resources the dwarves would not already be consuming (food, beds, &c)
- very safe
- no conflict with existing workshops or skills, unlike gulag or sweatshop
- dwarves gain no professional skills during this time, and their existing ones may rust
- lowers physical attributes due to rust
- produces no trade goods or useful items for the fortress
- produces many romances and tight-knit friendships, which put you at risk of suddenly having lots of Fun
- inter-dwarf personality conflicts can produce early misery and tantrums. This can be prevented with quality furniture and food, and the risk is eliminated once friendships and relationships are formed and producing happy thoughts.
- unless the entrance and path from the exterior are carefully set up, you will probably have to draft new dwarves and station them in the charm school to move them there; this will produce an unhappy thought that can exacerbate the early period of tension
 National self-defense training
Note: with the new military system, proper self-defense training is somewhat more complicated to set up, but allows much more effective reservist training once it's running. Make sure you're familiar with the Scheduling system before attempting this.
This is the process of training all your civilians in a basic military skill - or at least, most of them. Any time a dwarf is activated into the military, and they do not have at least Novice level in some combat skill, they get a bad thought. The easiest way to do this is to assign every new migrant to dedicated training squads, and assign that squad a barracks. Then, schedule these squads to Train one or more months in the year, and set all other months to "No Scheduled Order". Then go to the Squads menu and set the squad to "Active/Training". One month in six or one month in 12 will ensure skills don't get too rusty, as well as ensuring all dwarves reach a basic level in soldiering. To increase the rate at which dwarves gain skills, you can place one experienced soldier in each squad, which will make demonstrations much more valuable. It is worth setting the "Train" order in the schedule to less than 10 minimum; this allows dwarves to take time out to eat, drink, sleep...
Then, if they ever get caught where they don't want to be (maybe they bump into a thief coming around a corner, or a flying critter jumps them, or you need to urgently order them out of the path of a magma flood, or send them to the control room - anything), not only can you activate them with no bad thoughts, but every dwarf has a better chance at not-dying - which can only be a good thing. Moreover, idle dwarves will now go to "Individual Combat Drill" rather than standing around timewasting.
Note: if you're feeling cheap, training squads can be set to "No Uniform". This will teach wrestling. However, it's probably a better idea to churn out some training weapons, wooden shields and leather armour, as this will allow dwarves to gain the shield user and armour user skills.
- The charm school can cross-train many dwarves in the many mental attributes, but produces no useful items, trade wealth, or professional skills. The method is also still being refined and potential pitfalls may still be uncovered.
- Artillery training can give you some siege operators, which will be useful if you have ballistae.
- The internship only trains up one dwarf at a time. Your stocks could also lag behind if you are unlucky.
- The gulag requires planning, and your dwarves in the fortress proper may run all the way to the gulag to grab a stone for some crafts, a chair, etc. It does, however, train your dwarves in mining quickly, which is always a useful skill.
- Renovation is hands-free, but may bloat your fortress wealth too quickly.
- The sweatshop creates a large amount of goods, which can be traded away to keep traders happy. It also increases your wealth by quite a lot, which can be good or bad depending upon your situation. The goods are also difficult to manage.
- National self-defence training is easy to manage when set up and lets you give your civilians clothes and light armour to keep them safe. However, it can take valuable workers away from their job if the training is too frequent.
Note that the artillery training and internship don't take away strange mood potential (you can give those dwarves dabbling in anything you want and that's how they'll get theirs), while the gulag, renovation, and sweatshop do.