Tactics is of little use to anyone without an accompanying skill, but on the other side of the sword those weapon skills are also useless without tactics. Generally raised to grandmaster level for anyone wishing to engage in physical combat, tactics both functions to determine your hit chance, and applies bonus damage to your attack.
Unlike most skills on UO: Invictus, training with a NPC prior to beginning your path would most assuredly be a waste of gold. The simplest means of training this skill is to engage in melee combat while either unarmed or with a weapon equipped. The means of training this skill will require you to seek out targets with increasing levels of tactics to train your skills upon.
A common method of macroing this skill is to spar with a friend while cross healing each other with band aids. Both of your chosen weapon skills and tactics levels will rise along with each other until GM. Most choose this method while using some of the lowest damaging weapons such as knives, daggers and wands.