My advice for playing HU.
1: Within the first couple of hands, raise on your button w/any two cards. The goal of this is to see how your opponent will react.
2:However your opponent reacts, set your play to the opposite.
3: Take weird lines of betting. For example, if you flop trips, Check-Call, Check-Call, 1/3,2/3 of the pot.
4: People bluff a lot. So don't give up that easily, Especially on the River if the action has been light.
5: Play within your BR restrictions.
6:ALWAYS KEEP YOUR OPPONENT ON HIS TOES.
7: Do not fear betting out-of-position on dry flops.
8: My standard Continuation bet is 2/3 pot. Do this often. But i would recommend 2/3+ most of the time, 1/2 or less looks weak to most players.
9: I will say this, If you're like me, and you play an aggressive HU game, you won't always get the jump on your opponent, and you won't always run over people the way you want to. So if you lose 1-3 hands and your Aggro play is not panning out, SLOW DOWN. Limp from the button, fold your Blind to some raises. Look to actually make a hand and play a-b-c poker. At that point, it's about all you can do. Alright, Alright, due to a conflict in the responses, I'm going to make an extra note on this: If you cannot slow down, and aggression is also not working, then play fit/fold. And another note: This point is the most controversial. So I make special emphasis on this that it's just my opinion
10: IMPORTANT: THESE ARE ONLY MY OPINIONS, EXPERIENCE IS THE ONLY WAY YOU CAN REALLY IMPROVE YOUR GAME