I like to play as the Anglos, and after I get most of my units, this is what I choose:

3-4 Longbowmen(or archers depending on whem I'm at)
2 Heavy Cav
3-4 Light Cav(it sucks that I can't get mounted cav)
Remaining: Mix of Spear, and support infantry(Billmen, Mounted Sergeants...depending on when I'm at)

Basically, regardless of whether I'm attacking or not, I open up with a couple volleys with my archers, swing the the light cav /WAY/ to the side, position my footmen according to what I'm faced with and keep my heavy cav as reserve. When I see that one of my units is in danger, or that I see an opportunity I send in my heavy cavs. In the meantime, I use about half my light cav to attack the far flanks of the enemy, and the rest I use to ambush any fleeing enemy units or just send them against the rear of the enemy(whichever's best at the time).

Another favoured tactic of mine is to use my light cav to lead off some of the opponent's better units. (I once had a merc unit of mounted crossbowman lead off a 6-7 star ghulam general for the majority of the battle which is about the single best thing I did in that battle).

Also, I like using light cav as screens as someone mentionned, really, heavy cav I don't use all that often...Also, I only use some of my archers ammo, the rest I hold back for when I'm in the actual battle, I swing them off to the side, and pepper the enemy's flanks where the risks of friendly fire are minimal.

Also, I like making battlegrounds of like 1 heavy spear to pin down the enemy, and then send my support infantry(billmen usually) against the flanks of whatever unit(s) the spearmen are fighting.