Sleep face up if you can. Sleeping on your face or cheek can cause loss of collagen and elastin on that side, due to the amount of pressure placed on it for the entire night and the resultant moisture loss. For your duvet, I’d recommend sleeping on silk pillowcases as cotton sucks moisture out of the skin. Furthermore, it prevents skin from creasing - and the effects of ‘bedhead’ too from a hair perspective. Be sure to wash your pillowcases at least once or twice a week!
Don’t go to bed without a serum. The skin rejuvenates at night so opt for high tech reparative product. Oils and moisturisers can tend to be clogging or just sit on the skin, impeding skin turnover and increasing premature ageing.