Oh, and even if you think you are better than your opponent (unless its blatently odvious) dont underestimate them, be brutal and ruthless. A nice trick is to play easy on an opponent, so he takes you for a joker, and using easy but effective tactics wear him down till he dies, and just if you want to you can always just play your ultimate and see how they deal with you.
Oh yah, and play alot, on lan, with good ppl, you will be good in no time flat.