Block the Sun (in a good way)

When possible, choose sunscreens that physically block the sun (using minerals such as zinc oxide and titanium dioxide) in preference to chemical absorbers, which can have effects on the environment and possibly on your body. These aren't as common, but are available at places like Whole Foods, Jimbo's and Henry's.
Also check out
the daily green for more information on sunscreens

And an interesting video that might make you think differently about why to use sunscreen
. . . dear 16-year-old me