Since my early teens, I have become increasingly wary of the sun's ultraviolet rays and I pride myself on being careful to protect myself from both skin cancer and premature signs of aging. I was recently bragging to a friend about my wonderful skin care habits when he pointed out something that hadn't occurred to me: my sunscreen application was pointless if I wasn't reapplying it after two hours. Between the time I apply it in the morning and the time I break for lunch, the SPF has worn off. This made me wonder what other risky sun mistakes we all might be making without realizing it. After doing some research, I will never be caught with any part of my body unprotected again. Read on to find out how to use SPF from head to toe all Summer long.