For those who have very fair skin use a sunscreen with SPF 50 to prevent from burning. Fair skin to medium toned skin, start out with SPF 25 or 30 but when you become tan use SPF 15. Olive toned skin burns very rarely so using SPF 8-15 would be best. Those with darker toned skin, can use SPF 4 or 6. But, remember sunscreen doesn’t work if you don’t reapply every 1 to 2 hours to protect from harmful UV rays.
Information obtained from http://www.e45.com/main.asp?pid=3405