Washing your face twice a day, and regularly washing your hair are the best preventative measures.
For when they pop up though, most anti-acne face washes should work if you start to apply it regularly.
But I also swear by witch-hazel. You can get it in a liquid form which you dab on with cotton pads, or you can get witch-sticks, which are like little lipstick tubes you open and rub over the affected area.
That's all I can recommend really. Wash your face every day with soap/cleansing pads/anti-acne scrubs, particularly if you get sweaty. And wash your hair regularly enough so that it doesn't go greasy (if this means a wash every day, consider using a conditioner too, to prevent your hair going dry and damaged from too much shampoo).
And beyond that, bear with it as you grow up. Acne does get much more managable as you get older.
