Don't smoke. Smoking damages the microcirculation to the skin, making it dull, grey and lifeless. Your hair is affected in the same way. It also leads to the early formation of wrinkles, especially fine lines around the mouth. Many models smoke partly as an attempt to keep slim, but they are in fact wrecking their careers.
Keep alcohol intake to a moderate level, no more than 14 units a week. The most important thing is to avoid binges when you drink all your allowance in one go, which is particularly toxic to the liver.