Lay off the dairy products.
I've read that there is a strong link between the amount of milk consumed and acne. research suggests that although milk and other dairy products do not cause acne, they may be a contributing factor.
I haven't had milk or yoghurt for 3 years now. I can't say I had a notable difference, but due to the amount of medication my acne has slowly been improving anyway. However I did notice that if I did happen to have milk everyday (such as when I was camping for 3 weeks), breakouts appeared. When I was younger, I used to drink milk by the bucket full and I also had severe acne, so again, it may have been a contributing factor.
I still eat cheese, albeit infrequently, and occasionally cream, but there are many delicious substitutes for milk, such as soya milk, rice milk, almond milk etc and vegan cheeses.