i've had pretty clear skin but recently broke out a lot (about 7 months ago). I figured it was stress and lack of sleep, but my skin wasn't really improving, so i finaly went to the dermatologist about 3 weeks ago. He told me my acne (it's only on my forehead) was probably from my bangs (which i had cut at about the same time i started breaking out.. so makes sense..), and that i should just keep my hair out of my forehead. So make sure you don't have stuff touching your skin, including your hair, hands, etc - all of that can potentially clog your pores and cause you to get acne.
also, i wanted a quick fix, so the doctor prescribed me Benzaclin - actually, my friend was using this and liked it, so i asksed the derm. to write me a prescription. Anyway, I have been using that for the past 3 weeks, along with cetaphil cleanser and an oil-free moisturizer (dont let oil get on your face at all! I was using a very oily moisturizer before, and yeaa.. taht just made things worse), and my skin is almost totally clear =]