Played part way through one campaign before our GM got too busy to plan ahead, someone in the party started a new campaign as GM for us.
Two main things I've learned from experience:
1. When s/he can the GM [i12l]will[/i12l] be an @$$hole, it is expected.
2. [url=http://www.youtube.com/watch?v=waa2ucfgVgQ12l]NEVER SPLIT THE PARTY![/url12l]
Okay well there's a third thing to remember.... have fun with it! Do a little bit of everything... but don't take too long doing things or the party might get frustrated.