What do you want to get out of it? How many attendees do you want to stop at your booth How many leads do you hope to generate? How many products do you want to sell? Are you focusing on promotion or hoping to launch a new product?
You can have more than one goal, of course, but the point is that you need to be clear about what your participation in the trade show is going to achieve. Determine what your ROI would be – if one new customer helps you justify you being at the event, then focus on getting that customer.