If you do get sunburned.... which many people (myself included) do, even with sunscreen, one thing that really helped me was Solarcaine Aloe Gel. All the goodness of normal solarcaine without the pink goopieness (yes, that is a word in my world). Also, my Mom put it in the fridge before putting it on my very red skin, and the coolness helped, along with some damp cold facecloths/towels.
If you can, buy a small bottle of sunscreen (or use a random bottle that you have a home) so you can always carry some with you. If it's hot, you will sweat and your sunscreen goes bye-bye rather quickly.
I went from Snow White (all I need is the black hair, and I really could be her... it was my nickname for a little while) to lobster red in half an hour with spf 45... don't skimp out on the sunscreen, buy the best! Also, try sunscreen with parsol in it, it works much better than most of the sunscreens I've tried.