Since its inception in 1979, The Skin Cancer Foundation has always recommended using a sunscreen with an SPF 15 or higher as one important part of a complete sun protection regimen. Sunscreen alone is not enough, however. Below is a partial list of tips. Be sure to visit their website for the complete list and more great tips.

Seek the shade, especially between 10 A.M. and 4 P.M.
Avoid tanning and UV tanning booths.
Apply 1 ounce (2 tablespoons) of sunscreen to your entire body 30 minutes before going outside. Reapply every two hours.
Cover up with clothing, including a broad-brimmed hat and UV-blocking sunglasses.
Keep newborns out of the sun. Sunscreens should be used on babies over the age of six months.
See your physician or dermatologist every year for a professional skin exam.