Want to reduce the risk of skin cancer? Follow the rules of applying sunscreen.

Protecting your skin from the sun requires a little effort, but it's worth it to reduce the risk of skin cancer and aging. Protecting yourself, however, is much more than a few shots of sunscreen when you remember. Science shows that regular use of good sunscreen is the key to reducing the health risks associated with the sun. There are some simple rules to follow when it comes to sunscreen.

– Look for a broad-spectrum product that blocks the UVA and UVB rays of the sun.

-Choose an SPF (sun protection factor) of at least 15-30 or more.

-Use a quantity of "shot-glass" for your face and body (about 2 ounces).

-Remember to apply to your lips – they burn easily.

-If using an aerosol sunscreen, rub it on your skin after application

-Apply 30 minutes before sun exposure.

-Recrease after swimming, or every two hours when you are outside.

-Wear sunscreen every day, even in cloudy weather.

Who needs a sunscreen? Everyone! Regardless of age, race or gender, one in five Americans will develop skin cancer in their lifetime. The daily application of a high SPF (15+) sunscreen every day can help reduce this risk. Remember that sand, water and snow reflect the sun's rays, so wear sunscreen every day of the year.

Madelyn Fernstrom, PhD, is NBC News Health Editor. Follow her on Twitter @drfernstrom.