From my experience at stars

1. Agression works
2. More agression works even better
3. In cases when you run into a very agressive player you cannot let him dominate you - you will need to fold more but definitly call with any decent hand and raise with any good hand (Ax, 2 pictures, pair, etc...). You want to trap him in the hand
4. Most people lose patience in heads up, so if it goes on for more then about 10 minutes and you keep playing a good game they will make their mistake.