The following are the sun protection recommendations given by FDA:
Multiple sunscreen: in addition to sunscreen, you can wear long sleeved clothes, hats and sunglasses.
Apply sunscreen 15 minutes before going out, and reapply at least every 2 hours. If you swim or sweat a lot, apply it more frequently.
Apply enough sunscreen. Adults or children of normal size should use about 30ml sunscreen on their face and whole body each time (shocked? In fact, I am too).
Don't forget these easily overlooked parts: ears, nose, lips, back neck, hands, insteps, around hairline, and the part with sparse hair on the top of the head.
It is not recommended to use sunscreen for infants under 6 months of age. Infants can wear long sleeved clothes or stay in the shade for sunscreen; Children older than 6 months should follow the instructions. The American Academy of Dermatology recommends sunscreen containing titanium dioxide or zinc oxide for infants and young children over six months of age.