There are many reasons you might find yourself staffing a booth.  The industry trade show is a logical example.  You provide benefit plans for companies in that industry.  They have an annual state conference.  Your firm books space for a booth.  At the other end of the spectrum, your town has scheduled an auto show or crafts show.  There's an entire village of vendors with booths.  Personal services are included, so you booked a booth.  The rationale is "These people have disposable assets."  What do you do?

1. Location, location, location.  Talk to the organizers.  You want a high traffic location.  Ideally this is near the entrance to the event.  Your booth is the first one they see.  If not there, try to get a location along the first aisle.
2. Have a great booth.  This shouldn't be a problem.  Your firm should have access to professional displays built specifically for this purpose.  The displays might even come with their own lighting.  Plan in advance so the setup can be shipped to your office and you can get it on site.
3. The booth is always staffed.  Have you ever gone to a farmer's market or an antique center and seen darkened stalls?  It's a missed opportunity.  You will need help from your office.  You'll need enough people to always have the booth staffed, plus allow for someone to take a break (or roam) while their relief is covering the booth.
4. Lectures and workshops.  Does the conference include breakout sessions on the schedule?  Can you present a useful, educational topic?  If the answer is yes, make this a priority.
5. Give attendees a reason to stop by.  You've been to enough conferences to build a collection of water bottles and travel mugs.  These are logoed products.  Maybe you offer hand sanitizer or keychains.  You need something tangible that isn't a brochure.  They get your literature with the giveaway.
6. Gather potential leads.  Companies pay for booths at events for visibility, but also to gather prospects.  Exhibitors have been holding drawings for gift cards for decades.  People walk by, read your sign about the drawing and drop in a business card or fill out a slip.  "Winner doesn't need to be present."  You do it every day.
7. Go walk about.  While your associate is staffing the booth, you play the role of conference attendee.  Check out the other exhibitors.  Drop in your business card.  Make some connections.  Gather their business cards.  Everyone isn't a competitor.  Some are prospects. 
8. Is there a gift bag?  Conference attendees are often handed tote bags on arrival. They might include a map of the exhibition floor, an event agenda and some giveaways.  If you can get your company literature or giveaway into the gift bag, you will know every attendee has your material.
9. Publicity photos.  They get used in the local paper.  If the Chamber of Commerce has held this event, it goes into the Chamber magazine.  Dress nicely, smile, seek out the photographer or ask a friend or staff if you can get your picture taken.
10. Suggest prospects and clients visit you.  Your publicity material might offer the first 50 clients or prospects free tickets for entry. (This is sometimes a perk for exhibitors.)  You tell clients and prospects to "Stop by booth 123 and say hello."
11. The benefit of free food.  If allowed by the event, you might hand out free bottles of water or individually wrapped snacks.  Free food has been a draw forever.

The objects of exhibiting at an event is to raise your visibility and gather prospects.  Remember to focus on the mission!