This spring the following tactics are working to drive attendance:
Saturate the drive-in market. Give them a tangible incentive, such as "Free parking if you bring a copy of this e-mail."
Provide specific answers for what is keeping your target audience awake at night, such as new Federal regulations, foreign competition, etc.
Telemarket to a known list of qualified buyers with a specific message: "We are here to help you in these tough times and here is how...".
Promote right up to the end. Late e-mails should tout new and fresh content, such as a last-minute Keynote panel on "The Effect of the Andersen Breakup on the Widget Industry."
Expand the attendee experience, for example, separate networking receptions for SIGs (Special Interest Groups), such as Widget Production Engineer.