If you generally have oily skin type, it is difficult to change environmental factors to decrease oil production as it is a natural tendency for you to produce oil. You can wash your face frequently to reduce the oiliness.
There are aslso certain medical treatments you undergo to decrease the oiliness. One of the famous drugs is called isotretinoin, which is excellent in contolling oiliness. However, it is very difficult to decrease oiliness through lifestyle choices.