Slather on good lotion before you go out. Remember ears and neck, whatever is exposed. I used to ignore ears and got a nice basal cell for my negligence.
Main thing is check skin for unusual spots all your life. Melanomas often occur where you can't usually see them -- in the middle of your back, for example, and they can terminate you in a hurry.
When in doubt, have any suspicious spot checked, preferably by a dermatologist.