In addition to the sage advice you'll find herein this forum, you need to read your contract carefully and follow the rescission clause (near the end) to the letter, especially as it relates to the method of delivery.
Do not assume that you can use Fed-X, UPS or some other courrier, as sometimes US Mail is required by statute. Sometimes, certified mail is specified, and sometimes its "regular mail that is is reguired. If in doubt, use muliple methods to deliver your notice.