website programme-booklet during after
Communicate as much and as often as possible. It is almost impossible to do too much communication about your event. Keep sending messages, reminders, advertisements, encouragement, by email, via Twitter and every medium at your disposal.
Email and your website are the primary tools for communicating with your attendees. Remember that not everyone uses Facebook or Twitter or other social networks. If you rely exclusively on them you will exclude some of your own attendees.