Apply sunscreen liberally – at least a teaspoon for each limb, front and back of the body and half a teaspoon for the face, neck and ears. Most people don’t apply enough sunscreen resulting in only 50-80% of the protection stated on the product.

Sunscreens explained  http://www.skincancer.org/prevention/sun-protection/sunscreen

Protect your skin

For best protection, we recommend a combination of sun protection measures:

1. Slip on some sun-protective clothing – that covers as much skin as possible
2. Slop on broad spectrum, water resistant SPF30+ sunscreen. Put it on 20 minutes before you go outdoors and every two hours afterwards. Sunscreen should never be used to extend the time you spend in the sun.
3. Slap on a hat – that protects your face, head, neck and ears
4. Seek shade
5. Slide on some sunglasses