In an attempt to resurrect a long forgotten post, I wanted to pass along this tip that somehow never made it into my little guide:
Look for the less obvious shots.
I've shot a lot of airshows. After a while, all your shots just sort of run together and you end up with a lot of the same shots just from different shows. If you're so focused on the skies, sometimes you'll forget to pay attention to what's happening on the ground.