Stuff regarding who I am
I am an avid Dwarf Fortress fan who enjoys science-ing some aspects of the game.
 Training XScienceX
Unless otherwise specified, training occurs using unarmored humanoids in the arena.
Training the Wrestler skill
Doing so will raise Fighter at the same rate.
Training wrestling is very, very strange.
Wrestling can be trained from nothing to novice by grabbing and releasing a body part of an unconscious unit ~70 times.
Interestingly, 12 failed attempts to attack somebody with wrestling increases one's skill to half of novice (~20 experience per attempt), while simply grabbing and then moving away to release does nothing.
In an unrelated adventure mode incident, I snuck up behind a rhinoceros, grabbed its tongue, and attempted to pinch it off, raising my wrestler skill to proficient after many, many failed attempts. Oddly enough, the rhinoceros seemed okay with my actions, keeping the conflict level to "Brawl" and never turning around to look at me. At any rate, the gap between skilled and proficient took about 300 failed attempts at pinching the poor animal's tongue off (which took only a few minutes, since typing Aab<enter><down><enter> doesn't take very long), indicative of an experience gain of 3 points per unsuccessful attempt at past-grabbing wrestling damage.
Training Weapons Skills
Determined by using an iron spear on unarmored humanoids in the arena.
You cannot gain weapons skill from attacking an unarmored humanoid from behind or when it is unconscious. The amount of experience appears to scale according to how much of a threat your opponent is, which makes this incredibly hard to study. I think that using DFHack would help sort out this problem, since I think that it has an experience-checking command, but I am not sure, so verification by users of the program is greatly encouraged!!!
Pretty much the same as weapons skills. It seems a nice break of fairness from the often gritty tone of DF that you aren't incentivized to kick your opponent while it is down.
Watching a square grid of 36 unarmed, fully clothed humans gorily kill each other for over 3000 lines did not help train observer, ambusher, or tracker. When I turned on sneaking and started walking around, tracker and ambusher starte increasing, but not observer.
In contrast, by making 15 humans in the same tile (but otherwise with the same status) and attacking them all one by one, observer was trained. By the time I finished attacking them, observer was 3/4 of the way to novice, although I gained the skill at a far slower rate just by circling around the fight after attacking.
The skill gains experience along with archer. 17 iron breastplates being thrown trained a human to novice, suggesting 30 experience per throw. This did not change when throwing at other humans.Sadly, this did not change when the humanoid was unconscious. This did not change while throwing rope reed pouches instead of metal breastplates.
Unfortunately, this skill doesn't train when your opponent is unconscious and probably requires for you to actually be under attack in order to build skill.
Training Shield User
~20 experience per use, since it takes ~25 uses to reach novice. Hard to train in isolation, but probably trains fighter at same rate. Attacking somebody with a shield acts like weapons skills and trains Misc. object user.
Don't have anything else, yet.