Once you've found a product you like, be sure to use it correctly. The American Academy of Dermatology offers these tips for proper application.

Lay it on thick. Most adults need a full ounce of sunscreen to fully cover all exposed areas of skin. An ounce is the amount in a shot glass or enough to fully cover the palm of your cupped hand.

Apply sunscreen before you go into the sun. Sunscreen takes about 15 minutes to absorb into the skin, so put it on before you head outdoors.

Reapply sunscreen. Sunscreen should to be reapplied every 2 hours, even if it has a high SPF. Be sure to put more on immediately after swimming or sweating.

Don't use expired products. Sunscreen loses its effectiveness when it starts to separate, which happens 2 to 3 years after it was made. Toss any products that are expired, or that look gritty or have changed appearance.

Never rely on sunscreen alone. Cover up with sun protective clothing, including a hat with a wide brim and sunglasses. Try to avoid the sun altogether during midday.