If you get nauseous, Dramamine or hydroxyzine (vistrial) work very well to alleviate that, as does pot. Drink lots of water as this will help to keep you from feeling bad the next day (just like with drinking).
All in all, even if you're trip is kind of rough, you'll probably look back on it positively so just keep that in mind while you trip. It will be intense, but it will also be amaizing and I'm sure you'll have a good time. I have nothing but good things to say about my first time. I'm sure you'll be glad you did it, it can be truly enlightening. Even my worst trips have revealed startling and profound revelations that I wouldn't trade for anything.
Listen to Pink Floyd, it'll blow your mind.
Of course, your mind will be blown either way.