The most important piece of information on the save-the-date (other than who is getting married) is the date of the wedding. You don’t need to have your venue booked yet, but you must have settled on a date. The idea behind this card is to give your guests as much advance notice as possible so they can plan to be in town or at the location of your wedding.
For this reason, you’ll also want to include the city where your wedding will take place. If you plan to have a destination wedding, it’s helpful to send your wedding save-the-date cards a little earlier so guests can make travel arrangements.