Sunscreen, whether it's in a lotion or makeup, is your No. 1 weapon against the sun's harmful ultraviolet (UV) rays. The American Academy of Dermatology recommends using a water-resistant, broad-spectrum sunscreen, which blocks both UVA and UVB rays. Buy one with a sun protection factor (SPF) of at least 30. Apply it generously and don't forget often-overlooked body parts like your face, ears, nose and arms. Reapply it every two hours, or after swimming or sweating. For extra protection, also use lip balm with at least SPF 30.