I love heads up play, both cash and tournament and for nearly every game.
I don't know if there is any universal advice. Clearly, aggression is important and your hand valuation skills have to adapt to the situation. Where the jack high flush is an easy fold 9 handed when facing a pot-sized turn shove, it is usually a stack off situation when heads up (unless the guy is super passive and only gets in with better--which is a leak all its own). Generally, you need to get some experience to know what hands are worth what. At the start, you will make some calls or value-bets that seem laughable if you are used to playing 6+ players.
No one can tell you what hands are good/bad in which spots because it is very villian dependent. You have to get a feel for how the other player is playing and base your actions on that. Look for spots where they are folding too much or calling down too lightly. Folding too much is a huge thing at many micro heads up cash tables. In fact, I am willing to bet that you could beat those games by bet/folding every street. Just bet and fold if they come over the top. *
Tournament heads up is fun, but is also determined by hot/cold equity most of the time because stacks are so shallow. In the smallest games, this is still characterized by people folding too much. So stay aggressive. The difference is that when they come at you, you need to commit when your equity is right.
* I am not saying 100% bet/folding every street is the best way to play or will make you the most money. It probably isn't. I just have a gut feeling that you will do better than break even with that strategy because the majority of the players are folding way too often. You also will have some players wise up and take you to value town when they flop big, but I still think you come out ahead from all the times they fold to your 60%-pot bets on each street. I should run the numbers instead of going with my gut. But, I am relatively sure it will be close, if not actually correct.