Another vote for Organic Chemistry as a Second Language.
And I can't stress enough how important it is to practice reactions. When you get your text and start the class, do the questions and exercises regardless of whether your prof assigns them. You gain a lot from it.
And drown yourself in flash cards. They're my bible for classes like OChem.
And don't sweat it too bad. I went in to OChem with a sense of dread, having heard horror stories. Some folks found it nightmarish, but others thought it wasn't too bad. I found myself in the latter camp, and I'm not a particularly bright student. You never know.