They key to winning a heads up match is to pound your opponent once you have the chip lead. Now this doesn't mean they wont catch a good hand, but it will keep them from seeing a cheap flop and catching the nuts on a hand they normally wouldn't have even played.
If you find yourself in a position where you have a safe chip lead on your opponent, you need to turn up the heat and finish them off. Force your opponent to make tough decisions. They will be more likely to throw in the towel and go all in with a marginal hand if they have a short stack.
This does not mean you should push all in on every hand. Having a good hand is optional, however. You will soon realize if you haven't already that heads up poker is more of a mental game than it is physical. It is not always about the cards in your hand, and if you know how to make your opponent back down, then you can easily win.