What are good ways to stop peeling (after sunburn)?

Hydration/ moisture: Keep the area well moisturized (aloe vera can help the healing process). Don't yank on peeling layers of skin (ouch!) hydrate well with water.

Simple Care: Sunburn is response of the tissues to injury from solar radiation. It is simply inflammation which means increase blood flow to the area to promote healing. Do not use ice as this can injure already injured skin. Cool water soaks can help as can taking anti-inflammation medicines like Motrin or advil (ibuprofen). Avoid any further damage as this can cause scarring . Good skin cream applied daily/gently helps.