I use a 2 hander. usually an axe, but sometimes a sword.
-Better the weapon (+ skills) that allows you an almost sure 1 hit one kill (big axes and big hammers are niiiice).
-If you get the hang of it, aim for the soft spot of the opponent (if any), or is head. Medium to good armor and a scarf over the head? The head!
-Take good swings at the enemy, meaning:
-Don't stay put! Learn how to move, swing, dodge blows. The AI isn't that varied and usually makes a few mistakes (is quite predictable) - learn them.
-Sometimes you don't really need to defend yourself. Move in the direction of your enemies strike (the blow is coming from your right and cutting from there to your left? Go to your left - or some rare times, your right - it really depends), specially if he is using a bladed weapon. Often that is enough to get 1, 2 or even 0 damage points - if your armor isn't too ****ty, of course.
-If he is piercing you or using a blunt damage weapon (and he is powerfull enough), then it might be a good idea to block him, or avoid the blow altogether...
-If the enemy has mostly spears you don't want to run directly towards him, specially if you're alone. You can circle him and fall back or just circle him/them. Keep striking..
-If necessary, and in dire need, take out your shield (carry a shield on your back. Good for the sissy archers and for such situations as these). Try to get some distance from your enemies before you can strike again with your weapon.
-If you notice you are as fast as your enemies while they are advancing and you're retreating... then you
are faster then them. Need I say more?
-If you have more troops, but they aren't by your side, call them. They might create the caos around you in order for you to make some kills or get away from danger.
Hope it helps... I'll write more if I remember.
PS: Oh, and none of these are rules of engagement. Sometimes this stuff doesn't work, or - it doesn't work in every situation. Make up as you go along