Ok, I had my first shroom trip tonight and it was amazing so I'll tell you what precautions I took.

1) Have a sitter (who's sober preferably, or stoned, either one is fine, unless they get completely stupid when they smoke)
2) Make sure your sitter is someone you get along with and can stand to be around for at least 6-8 hours.
3) For your first time I wouldn't recommend anything over an 1/8.
4) Be in a surrounding with plenty of interesting things to do or experience. Whatever you enjoy, be it: music (of course thats a given), pen and paper, video games, tv, something fun to try and do.
5) Don't drink any alcohol (unless you start to have a bad trip, my sitter said this will calm the trip down, I'm not sure if thats true or not, anyone else on the boards care to comment?)
6) Be in a really happy mood. If you're dwelling on something that makes you nervous, anxious, sad, depressed, angry, or paranoid it's likely it won't be a fun trip. Be really excited about taking the shrooms. Don't be nervous.
7) Prepare to get fucked up.
8) Chill and enjoy.
9) I <3 the Magic Mushies!