Before he accepts it**
Removing friend request

You can't.
Yes you can. Well, you can't guarantee they won't see it or get a notification but you can cancel it. I do it all the time when I accidentally hit the button on my phone.
The easiest way is to visit their profile and click the Cancel Friend Request button.
You can also go to Share > Friends and click the Friend Requests link. Then find the member under Sent Requests and cancel there.

I've been a 'friend' with someone for months because I accidentally sent him a friend request and he seemed so happy when he accepted it. I haven't talked to him since then but if I cancelled now he might ask me what he's done wrong and it would be embarrassing.
How can I remove a friend request I already sent before the other guy sees it?