If you just want to shut down your account for a little while, with the option to reactivate it later, you can deactivate your account. This is simple: just go into your account settings and click on the “deactivate account” link. This immediately makes your account invisible to everyone else on Facebook. If you decide at a later date that you want to reactivate your account, it’s as simple as reactivating.
If you’re looking for something a little more permanent, though, you’ll need to submit a request to Facebook. The tricky thing here, though, is that they don’t immediately delete your account, and if at any time before it’s permanently deleted you log in or otherwise interact with Facebook, your deletion request will be canceled. For that reason, it’s a good idea to go around to any computers or devices (like your mobile phone) that you access your account through and log out (deleting saved passwords is also a good idea to prevent an accidental login).
Then you can use the form found here to request deletion. Remember not to log into your account at any point after that. There doesn’t seem to be any official notice on how long it takes, but unofficial reports say 14 days. To be on the safe side, you may want to wait a month or more before attempting to login to confirm your account has been deleted.
Details at: www.smashingmagazine.com/2010/06/11/how-to-permanently-delete-your-account-on-popular-websites/