You know the drill: avoid the sun between 9 a.m. and 3 p.m., wear a high-factor sunscreen and cover up with long sleeves, a hat and good sunglasses. But this isn't where it stops – you also need to get well acquainted with every inch of your skin.
Most people know the importance of keeping an eye on the heavily pigmented spots (e.g. moles), but you need to extend that scrutiny to any suspicious spots. A good idea for keeping track of moles and other possible ‘sun spots’ is to photograph them periodically, then compare the pictures for any changes. Don’t forget about those bits you don’t usually see, like your back: get a partner or friend to check on the spots you can’t easily see in the mirror.