Always Use Sunscreen
If you make a habit of layering on the SPF when you're young, your skin will thank you for it years down the road. Liberally apply the sunblock when you know you'll be out on the beach all day, or even just out in the sun for 30 minutes. It only takes a few minutes, and dramatically decreases your risk of developing skin cancer. Your skin will also age better if you take measures to protect it.