As soon as you receive a gift, you should send out a thank-you note. As hard as it will be given the many notes you will be writing, try to be as warm and personal as possible. Always mention the gift and (if possible) how you and your fiancé plan on using it. This small touch will prevent people from feeling that you just sent them a form letter (which is completely unacceptable). When sending notes for gifts you receive before the wedding, sign with your maiden name.
When writing a thank-you note for gifts of cash, checks, or a gift toward your honeymoon registry, the amount of the gift should not be mentioned in the thank-you note.
The gifts may start arriving as soon as you announce your engagement and can typically continue up until one year after you are married. Setting up a gift organizer will help you keep a record of what you receive and from whom and when. Organizing from the beginning will help when you sit down to write all of those thank-you notes.