"Strategy without Tactics is the slowest route to victory. Tactics without strategy is the noise before defeat." - Sun Tzu
Tactics works the same way Evaluate Intelligence works with Magery.Warrior templates with a weapon skill will do significantly less damage without Tactics. Every warrior should pick up this skill to deal more damage.
Please note that Tactics does not work with Wrestling
Tactics is trained the same way as all the other fighting skills are trained. Simply pick up a weapon and hit things.
Your level of Tactics determines how much of your Base Damage you are capable of inflicting on opponents. The percentage is equal to your skill plus + 50% (for example, at 120 skill points you will deal 170% of your base damage, while a fighter with no skill will only deal 50%)