Your first question should be: 'Why are we going?'
At the end of the day, what would "success" actually look like? What things would have had to happen that would make you think this event was a good one?
Experience has shown that there are four areas that serve as the cornerstones for nearly all show objectives - and, for that matter, all marketing ventures. These are typically tightened down with measures and assigned strategies that enable reaching them.
1. Increasing sales and reinforcing market share
2. Increasing share of customers and getting current customers to buy more
3. Introducing new products
4. Positioning or repositioning your organization, its brand and products