A BIG thing that people don't realize too is the cleanliness of your pillow. I mean, most people go weeks without washing their pillow. It gets dirty, and that dirt gets into your pores while you sleep, creating acne. A solution to this is to put a towel over your pillow, sleep like that for one night, the next night flip the towel, then the next night change towels, repeat. That or you could change your pillow case every 2 days (each night sleep on a different side).
I did this myself, and I noticed a HUGE change. I don't have acne anymore, and haven't in a long time since I started this. All of the other solutions above help too though.