Save the date tags are a great way to let friends and family know about your special day well in advance.
With wedding planning taking a considerable amount of time it is likely you will know your date and venue months in advance.
Sending a save the date card gives you a much better chance having everyone you want there on the day and your guests will be anticipating the wedding invitations once the time comes to send them.
Send up to a year in advance or even in the months before your invitations if you have less time.
Include the key information. Your names, date and venue/location.