I did fairly well in all three of my P Chem classes, and what I did was keep on top of the material. Basically, I picked out some problems and worked on them. When I had problems with HW or examples, I went to office hours. That's key to any class. Go seek help; that's what they're there for. Just to prove how helpful it is...by the end of the semester, my professor knew my name and the others who came to see her in a Berkeley class of 150. (I say Berkeley, because it's such a sea of students, you totally get lost). My advice: Don't stress too much. Just stay on top of it. Teach other students, cuz it's not only nice, but it helps you firm up your understanding.