Tactics is a combat skill used to calculate damage done with weapons.
Raising Tactics: Tactics has a chance to increase when you successful strike an opponent.
Gideon's Advice: Follow the standard advice for raising any weapon skills. For training of weapon skills, it is best to have two characters fight each other and bandage each other and use Anatomy on each other. Use a fast weapon to trigger more attempts at raising Tactics (bow, wand/blacksmith hammer, dagger, butcher's cleaver). GMing your Weapon Skill, Tactics, Anatomy, Healing, and Parrying takes little time on UOR doing this. I would recommend gathering a lot of wool and/or cotton and making it into cloth before doing this to save money. Please note that Tactics can lag significantly behind a weaponskill. I would recommend that if you've already GM'd your primary weapon skill, switch to the fastest and cheapest weapon you can and attack an opponent with zero skill so you land every attack.