The dark industry secret is that registration figures never equal actual bodies on the floor. For many shows there is a 40% to 60% no-show rate for those who pre register free for the exhibit.
You should have a separate promotion plan to persuade more pre-registrants to actually come to the show. This is money well spent. Some tips:
Build the buzz. Communicate with pre-registrants early and often—and keep the information fresh. Tell them all the great benefits of attending.
Find the right hook. Give them a concrete reason to come: killer Keynote; free tee shirt to first 500 each day; a copy of the latest Widget Design Manual, etc.
Get help. Encourage exhibitors to communicate with pre registrants to motivate them to visit their booth. Offer the pre-reg list free or at a discount.
Keep at it. At 3:00 p.m. on opening day, send an e-mail or fax to all no-shows within 200 miles. Tell them what they missed today and why they must come tomorrow. Refer them to a special page on your web site for last-minute details.