As with other forms of marketing, target your audience, not the whole world. One of the biggest mistakes people make is exhibiting at shows that do not draw their potential customers. Determine all of the costs involved. This includes staff time, per diem, travel, materials, etc. Then find out how much business you must generate to profit from the show.
Trade shows keep statistics on the backgrounds of the attendees.
Use those numbers to project whether enough qualified people will attend to make the investment worthwhile. The Small Business Council, the Department of Commerce, and your state government can help you locate trade shows. Send letters to your current customers inviting them to see you at your booth. Include free exhibit tickets if possible. If you are introducing a new product, be sure to send press releases to magazines that publicize the show.