Thanks? You don’t need to make it all that complicated I don’t think, unless it’s the President or the Pope or Michael Jordan, or someone like that who has accepted your friendship request. Sometimes a simple “Thank you” is all that is needed in that sort of situation, if you feel the need to thank someone at all.

Send a message saying… “Thanks for accepting my friend request”

As per @Odysseus – but if you decide to do so, do it in private. It’s just spam on someone’s wall. At least I don’t like messages like that on my wall.

Send ‘em a note—message on FB.

A simple “Thanks for friending me” by private message.

I tend to go with a “thanks for the add” comment on their wall.