It's hot and humid so wearing the right sunscreen is important. If you don't apply the right amount of sunscreen, you're not getting the protection you need. Dermatologist Jeannette Graf recommends using a nickel-size amount for your face and two shot glasses' worth on your body. If you're going to spend a lot of time outside, slather it on everywhere even if you plan on wearing a bathing suit or clothes—and do so at least 20 minutes before you leave, so it has time to sink in. "If you wait until you get to the beach to apply it, your skin will be vulnerable while it penetrates," Graf says.