Knowledge skills are like Profession and Craft skills in that there is no listing. I have not read Free Companies yet, but I'd guess that there is no write-up for Knowledge (tactics).
Basically, knowledge skills are wide open. You could put points into any number of obscure or unusual skills. For example:
Knowledge (Turanian Law)
Knowledge (cattle lore)
Knowledge (basket weaving)
Knowledge (military history)
Knowledge (Acquilonian legends)
Knowledge (lost treasures)
Use the skill points to reinforce aspects of your character. If the GM is good, he'll work them in so you can use them, and thus not waste skill points. For example:
I draw up a character, say a Hyborian soldier. Now, to add a little flavor, I'll say that he came from a poor noble family and received an education. While the family fortune was long gone (that's why he's a soldier..) the old library was intact. The soldier grew up reading heroic sagas of Acquilonia's greatness and hopes to restore his family's fortune through a military career. So to emphasize this, I'll put 2 of his first level skill points into Knowledge (Acquilonian Literature).
Will this help him as an adventurer? Not likely. But the GM will see it, and maybe work that into an adventure.
It can also be somewhat humerous. If your character likes his wine women and song, put some points into them as knowledge skills.
Knowledge (Taverns)
Knowledge (Brothels)
Knowledge (Ales and Wines)
Then of course, there's the ever helpful Knowledge (social diseases), which is good to have when the barbarian gets a funny rash under his loincloth...
