The only relevant definition of a successful show is a ton of qualified attendees actually on (and spread all around) the exhibit floor. Here are some tips on how to do that:
Prepare an actual plan to accomplish this—do not leave it to chance.
Have exclusive exhibit hours that do not compete with any other event—for example, 11:00 a.m. - 2:00 p.m. (with lunch on the floor).
Put all attendee services inside the hall, including the cyber cafe (do not put it in the reg area).
Ask the conference speakers to mention the interesting things that are on the exhibit floor ("Don't miss XYZ Widget in Booth 1234").
Convince high interest exhibitors to locate in the rear of the hall (you may have to offer them some incentives).
Create meeting room(s) right on the exhibit floor and schedule cutting-edge sessions which are free to all attendees.
If you use games or a "treasure hunt," be sure they relate to the interests of your atendees (such as solving a math puzzle for engineers).
For a prize drawing: make the prize relevant to the audience, require the winner to be present and do the drawing in the back of the hall during the last hour of the show.