One of the ways I use Lore "Tactics" (not sure if this is the same as military tactics- don't have the book in front of me) is to augment skills or situations in which a bonus mod is already provided.
So if a PC is able to arrange an ambush/surprise attack or manage to gain higher ground, or even perhaps organize a charge or co-ordinated advance on an enemy, I might award the crit Tactics skill bonus to attacks. The PC needs to explain/declare why he is trying to apply it, and I do have to say no some times, but I generally allow it.
I also generally only allow it once per tactic per battle. So once a PC gain high ground using Tactics, he gains the Tactics bonus for the first round. No longer. The same with a surprise attack (obviously), or unexpected charge.
Under certain situations I may even let the tactics crit bonus be applied to other characters the PC with tactics directs, but that is rare. An example of that would be "provide cover fire from hiding with your bow and target the big guy,". The first round, the accomplice might gain the tactic (al) advantage.
I don't like skills to just sit on the paper, I like to challenge the PCs with ways to use more than just combat skills, even in combat situations.
Hope this helps.