Mystery Shopping Yourself
So you've hired temporary workers to provide a presence for you at a trade show, you're not there yourself since you're networking with other business leaders at the event, so how do you know that the 'fort is being held down'.
You, or an event management company, might have hired temporary show workers - or your office staff might have stepped up to the social outgoing role of promoting your product at a trade event. This presents some issues. The temporary workers might not know all the details of your product, and have no consequences for being half-arsed. The office workers will be outside their comfort zone, and aren't used to approaching random strangers.
A way to monitor this, is to ask a valued friend (who the team have never seen you with), so to and sit/loiter near the stand on their own. And see how long, if at all, it takes one of the team members to approach them. The you can test to see not only how pro-active the team is, but what content they engage over.
All too often I've seen companies setup grand events in public parks and trade shows, only for the hired staff all to stand in a group in the corner chatting about their weekend - rather than seeking customers and promoting the product. I've been to events myself specifically to see a particular company, and got such a sour impression of them when I've approached their stand and recieved no acknowledgment whatsoever while the stand members just fiddle with their stuff or chat to each other.
Staff should always be spread out, in amongst the crowd of people - wearing highly visible branded clothing. Normally having the text 'talk to me about (x)' for example, to give the most approaching impression as possible. Well in advance of the event itself, the workers will need a good practice at this. Run a role play session to make sure everyone is on-board and knows that the script is.