Being aware of your own limits for starters.
Try and kill the ones who are unaware, and avoid getting into massive groups of enemies who will mob and slow you down. If there is a particularly troublesome opponent, do not be one of the many stupid cav players out there and keep circling him to try and kill him, and instead just run off (Speed is an advantage, so always use it) and go kill some other player.
Playing a slow ring-around-the-rosie of a single opponent when there are a few dozen remaining enemies is a sin too many cav commit.
If there are a half dozen team mates mobbing a single guy, do not be a prick and run into them to try and add one more kill to your count. Learn how to play smart and do a well timed cav bump to the enemy for your team mates to exploit while he is getting up from the ground, and learn to not run over your own team mates.
Being greedy as an infantry hurts team mates, being greedy as a cav kills them.
A great example would be BlueGreen who is one of the best armored cav players I have seen on any server. Never allows himself to be stuck, never slows down, always moves to new places, and knows when to switch weapons or avoid people with pikes.