The sun's ultraviolet rays are strongest during the midday hours (10 a.m.-4 p.m.); exposure at these times should be limited or avoided. When outdoors, cover as much skin as possible with a hat that shades the face, neck, and ears, and a long-sleeved shirt and long pants.

Sunscreen comes in various strengths, graded by the solar protection factor (SPF). Use a sunscreen with an SPF of 15 or higher. Because of the possible link between severe sunburns in childhood and greatly increased risk of melanoma in later life, children, in particular, should be protected from the sun.

Early detection is critical. Recognition of changes in skin growths or the appearance of new growths is the best way to find early skin cancer. Adults should practice skin self-exam regularly. Suspicious lesions should be evaluated promptly by a physician.

Basal and squamous cell skin cancers often take the form of a pale, waxlike, pearly nodule, or a red, scaly, sharply outlined patch. A sudden or progressive change in a mole's appearance should be checked by a physician. Melanomas often start as small, mole-like growths that increase in size and change color. A simple ABCD rule outlines the warning signals of melanoma:
- A is for asymmetry. One half of the mole does not match the other half.
- B is for border irregularity. The edges are ragged, notched, or blurred.
- C is for color. The pigmentation is not uniform, with variable degrees of tan, brown, or black. - D is for diameter greater than 6 millimeters. Any sudden or progressive increase in size should be of particular concern.