Wash your face at least 2-3 times a day with mild soap and water. Then use isopropyl (rubbing) alcohol on a cotton ball to further cleanse all the pores of your skin. This both breaks-up the oils from clogging your pores and also kills the bacteria that are infecting them. I used to carry around a little bottle of alcohol and a few cotton balls and do this part of the cleaning several times a day -- it really helped.
Keep this treatment up for at least 3 months after all pimples have disappeared, to make sure you have killed off ALL (not just MOST) of the bacteria.
Do not use any kind of oily skin conditioners or other products on your face until after the pimples have been completely gone for several months.