Get lots of exercise! How many athletes do you see with acne?
It's seriously the best thing you can do. Don't wear a hat unless you jog and live in Australia. Synthetic fabrics can oftentimes prevent your skin from breathing properly so if the acne is on the rest of your body, take care with what you wear. Also, don't use harsh detergents on your clothing and especially not on your bedsheets. The chemicals can make things worse.