When I'm heads up, I like to be the aggressor. I'm raising Any pair, any ace, any king, Q8+, connectors 78+, suited connectors 45+. Most of the time, I'll win the blinds. Lots of people play like crap heads up. If I can get a read on them, I'll widen my open-raise standards. For example, the last SnG I played, I got heads up against a nit who mostly folded to my raise. If he called the raise, I knew he had a small pair or a K. If he pushed all-in, he had an ace. Made it to where I could raise any two cards and release if he pushed on me (Unless I had an Ace as well.) Also, I have found it helpful to give a few walks with my weakest hands. It shows that you are not playing crap cards all the time. And, your opponent might give you a few walks as well. But only do this with your weakest hands.

Basically, try to see a couple of cheap showdowns early in the HU. You will get to see how they are playing certain hands and can adjust your play accordingly.