Cavalry charge before or after infantry engages?
Having a superior archer line and the infantry composition makes a difference in how best to use cavalry.
The enemy has better/more archers, same infantry levels: Go and slaughter the archers, sure your footmen will get more losses to their cavalry, but a freely firing archer line, if they aren't Nords, can be devastating.
Same archers, more infantry: Try joining the fray on the flanks, or even better from the rear. Wherever their infantry faces to deal with, they will be vulnerable from the rear to the rest of your army. In this case fast death dealers (short weapon, nasty swing) will be much more useful.
If they have hard hitting cavalry the best you can do is to engage them with your own. A close matched infantry skirmish can fast become a massacre with a bunch of heavy charging cav with spears, as these tend to keep the enemy -you!- at arms length while their buddies slaughter those who fall down from the initial charge or the impact of horses when things become a giant melee ball. If you send your cav to meet theirs however, your footmen will have more time and chance dealing with their enemy.
If you are Nord, and it sounds like you are, then your guys have slow horses. That means your companions will have to be more active in mopping up the light armored foes. To this end, I'd suggest lance/shield combo, and on your part, constantly looking up where you can strike hard. Your cavalry still should function according to the cases above.
My strategy is putting my archers on a hill and my infantry about 10-15 paces in front of them. Then I order my cavalry to follow me and we flank until we get behind their army. Then I order my infantry to charge and my cavalry to charge. Thus,their army is being attacked in two opposite directions. Boom they get wrecked. I recommend Swadian Knights, Nord Huscarls and Rhodok Sharpshooters