What you put in your body helps to reflect what's on the outside, drinking lots of water and eating healthily will help, ditto enough sleep and cutting out stress.
A proper facial could give you a kick start and finding the best products (or lack of products) for you skin. Different skin needs different things.
Depending on whether you are made or female - a good skincare routine is key, keeping your skin clean and hydrated without subjecting it to a load of chemicals.