Don't worry if you accidentally sent a friend request on Facebook, or changed your mind after the fact: unless the other party has already accepted or rejected (ignored) your friend request, you will be able to cancel it, or "unrequest that friend": this doesn't unsend the pending friend request, but it deletes it. There are two ways you can unrequest a friend on Facebook: a fast way, which doesn't always work, and a slower way, which always works even with the new Facebook. We'll start with the bulletproof way to cancel a friend request.
The most reliable way to unrequest a friend on Facebook, or unsend / cancel a friend request you have already sent, is to go through the privacy settings and block that person:
Behind the scenes explanation: temporarily or permanently blocking a user will cancel pending friend requests ("friend suggestion") you sent, because you cannot add as Facebook friend a user you blocked.
If the person has kept their default Facebook profile settings, they will receive an email notification like this to accept or deny the friend request; if this is the case, and they click on the link to confirm or ignore the request, Facebook will display a "You have no active requests" message:
While you cannot "unsend" a friend request, it is possible in some cases to unrequest a Facebook friend, or cancel a friend request (hopefully) before the other person sees it - follow these steps:
Either way you chose, we hope that you were able to cancel that request before the potential friend found it, and successfully unrequested your Facebook friend request!