Combat

The first rule of combat is to never let it become a proper fight. You're trying to survive and eventually make a living. Getting stabbed does not help you accomplish these goals. Planting an axe in their skull from behind while they are collapsing from exhaustion is much more effective.

Knock Down
Clubbing people in the legs appears to have a good chance of knocking your opponent down, which will give you the chance to do more hits or run for it if the battle is turning sour. Stronger attacks to the legs can even put an opponent down for days if they survive further combat.

Mobility
If it hasn't changed, every point below 100% mobility reduces your skills by the appropriate amount. So at 94% mobility, a skill of 67% is actually a skill at 61%. Taking those few minor hits at the beginning of a battle could lead to more crippling wounds as the battle goes on. So drop those 80 lbs of meat before heading into battle; it won't go anywhere.

Block or Dodge?
Blocking uses your weapon/shield skill, so if your block ability is higher than your dodge ability, make use of it. Dodging however, allows all damage to be avoided if successful and also prevents damage to valuable weapons by keeping them out of unnecessary clashes.

Counterattack
Counterattack is an aggressive way of reacting while in combat. You can dodge and counter at the same time instead of just dodging an opponent's attack. The way to deal damage is the same as a normal attack. But be careful, both you and opponent could be damaged at the same time while you are trying to counterattack, so if you are already hurt then try not to use counterattacks since they are more difficult to use than normal combat maneuvers.

Ignore
Ignoring an opponent's move is very dangerous because you would get hurt even when an opponent makes a sloppy attack. If you don't want to waste your turn NEVER use it.

If you are wearing very heavy armor, and want use bows in close combat you may want to chance ignoring your enemy's attack. Ignore can also replace counter-strike and blocking to prevent dropping your weapon, though dodging is almost always a better option.

Position
Facing doesn't seem to affect damage dealt since if they see you, they're already facing you. Attacking when you're undetected (Hiding) means the game won't factor in their dodge skill (Though hiding doesn't seem to work well in the current version). However, if YOU get attacked from a square that you can't see (Darkness or being attacked from behind) you will ALWAYS get hit. In short, NEVER turn your back on an enemy while within melee range. Because of how debilitating even a single injury taken can be, all attacks should be made from behind to inflict more damage or kill before your opponent can react.

Targeting
Attacking different body parts has different effects on an opponent, regardless of what they may be. The legs will always affect their mobility and head-shots will almost always be more likely to kill an opponent outright provided they make contact. For humans, injuring the arms will affect their ability to hold and wield a weapon in the affected arm while most animals can be lamed or downed if a foreleg or wing is damaged enough. Generally, if the outcome of an attack is uncertain, the body is the best part to target since it is the easiest part to hit.

Targeting priorities can change considerably if your opponent is wearing armor. Armor on any part of the body can make aiming at those parts undesirable for fear of damaging a weapon unnecessarily, or having an attack completely stopped by the armor and wasting a turn. To avoid this, learning the coverage of different types of clothing and armor is vital. As a general rule, however, the neck will usually be the most vulnerable point on an armored opponent, even compared to the potential of instantly killing or knocking someone out with a blow to the head or the completely unarmored eyes. This is due to the general rarity of hoods and coifs compared to caps and helmets.

While incredibly unlikely to happen, attacks to the head can strike an opponent in the eyes, reducing their vision in the same way as it affects the player. If both eyes are hit, this will completely blind your opponent and cause them to flee continuously until they are killed or one of their wounded eyes recovers enough to see. This does not keep them from trying to counter attack if you continue trying to hit them from the front, but it does keep them from turning towards you to defend themselves if they are attacked from behind.

Multiple Combatants
Being attacked by multiple enemies doesn't seem to increase the chances of being hit, but it does multiply the danger of getting flanked. Each attack will get rolled separately, which can exacerbate the penalty you get from fatigue.

Starting with 3.13-p1, every enemy after the first one that is next to the player will lower the player's combat skills by 10%.

Tip- if you're in a village and want to clear it out find a small house with no windows at the bottom of the village, make sure no ones in it and stand in the doorway (that way no one can come up behind you to attack)-(warning be prepared to face up to 3 combatants at a time and up to 12 total) hold (...)(period) until people appear in attacking view. After you think you've gotten everyone hold [.........] to confirm no more combatants. (keep the village as your own)

(Always make sure the village isn't joined to other villages) (make sure you have a fine-masterwork weapon such as a battleaxe, warflail or a kaumolais spear) (always use good protection)

NPC's will not enter water, to clear out a camp/town that borders water, step out 2 squares into the water so there is one square of water between you and the bank. no one will ever come within melee range, throw any ranged weapon until they are all dead.

Equipment
As mentioned before, good weapons and thick clothing are important factors to take into account. A powerful weapon can end the fight after a single attack, cripple an opponent for an easier followup, or at the very least shorten the length of the fight. Edged weapons (primarily swords and axes) leave the most devastating wounds, bleeding and nearly separating limbs is not uncommon with a clean hit. Piercing weapons (primarily daggers and spears) can cause bleeding to a lesser extent but will usually create less deadly wounds. Blunt weapons (primarily clubs and flails) bruise and crush, are even less likely to cause bleeding, and the more powerful ones are usually more effective against armor than other weapon types. Keep in mind that most weapons are also able to inflict lesser degrees of other damage types, like most swords being able to stab and spears being able to bludgeon and sometimes cut.

Ranged weapons are much the same as their melee counterparts, with a few differences. Throwing rocks and javelins is simple enough, but even a thrown rock can be unexpectedly effective. Bows and crossbows are generally quite powerful, and a skilled bowman or crossbowman can usually kill or cripple their target even through their armor before they come anywhere near them.

Another key difference with ranged weapons is cover. Anything (Watch out for your dogs!) between the shooter and the target has a negative effect on the accuracy of the projectile. Additionally, terrain features (trees, slopes, rocks, etc) within one tile of the target will also act as cover. In a shootout, your target should be out in the open, away from anything that could block your rocks or arrows while you should be hidden away near cover of your own.

The size and speed of your target is also important towards your accuracy. A small bird fleeing through the air is nearly impossible for even the best archer with a masterwork bow to hit, while a grazing stag is difficult to miss. For human targets, who can range from 40-250 lbs, there is no real way to judge this factor besides whether they are running (fleeing or aggressive) or not.

All clothing provides some protection against damage, though simple cloth will obviously not defend as well as proper armor. Total protection is also difficult to acquire. Unless an attack is particularly weak, most weapons can usually cause at least light injuries through armor and damage the armor as well. Because metal is irreparable, leather and furs are usually preferable over mail, lamellar and iron.

Resources
Most of these came with disclaimers about being outdated, however they may give you a view of what weapons do what

weapon table

armor table

thoth's weapon table

toth's tribes table