Depending on the type of meeting, promoting it may be as simple as sending a letter of flyer to attendees to announce what will be covered at the next meeting. Other events - a three-day educational conference, for instance- that could require several direct mailings to attendees.
Include the registration form or card in the materials you send out. Be explicit about your deadline for registration, as well as who attendees should contact for hotel and airline reservations.
This is also the time to determine what signage you'll need at your meeting. Signage is very important to avoid confusion and misunderstandings during the meeting. Don't assume that your attendees will just figure out where to go. Also, determine who will be supplying name tags or badges.