How do you counter in AC Brotherhood?

So i was playing ac brotherhood and i went up to stun this guy, hwever he somehow countered my stun and killed me, i was curious as to how you do this, also i need to know the proper way to dodge, one time i was playing manhunt and i succesfully dodged 4 kills in a row by using LT+A. however, since then i havnt been able to replicate that, your help is appreciated