Form follows function based on your objectives. Branding? Technology leadership? New product launch? New market entry? Qualified lead generation? I've purchased used booth structures, hosted workshops, made deals with organizers, had partners pay to be in my booth, and 'borrowed' budget from direct mail/advertising to promote attendance. If cost of booth space = cost of a person to register to attend, I've had sales pay for booth space and given them the free registration, since they were going to attend anyway, and make them spend a few hours at the booth. This is an area where you can be very resourceful!