I'll preface this with the disclaimer that I don't and never have had a major acne problem, but at 32, I still had minor ones until I changed what I was washing my face with. There's are a couple of products that I use now that in less than a month, cleared up my skin entirely (and I haven't had a single blemish in over 2 months).
Desert Essence face wash in the morning, followed by Burt's Bees Tomato Toner and any OTC daily blemish treatment, and during the day or evening, Desert Essence Cleansing Pads once or twice a day. The Desert Essence products contain an anti-bacterial ingredient that prevents pimples from forming in the first place, the Tomato Toner has natural acids that exfoliate your face and help minimize scarring or blotches and the daily blemish treatment (any of them work, I used to use Oxy Balance sensitive skin treatment to cut down on dryness) will clear up any of the minor ones that escape the first two items.
Stress, being tired and not eating right or drinking enough water will all contribute to acne problems, as does any kind of rubbing on your face (like resting your chin on your hands). It may seem kind of girly to use the Toner, but when I only used the other two products, some pimples snuck through. It really makes a difference.
You can get the Desert Essence stuff as well as the Burt's Bees toner at
http://www.mothernature.com.