(VP, 317Consulting Services)
So many sales people don't have a plan for this situation - amazing! As you've probably seen as well, some teams will attend a trade show with the greatest of intentions, but they have no follow-up strategy, and the cards they gather at the show end up in a shoe box as a door stop (literally - I've actually seen this happen).
Have a plan before the event - know who you're going to see & why, and plot your follow-up strategy based on the kind of customer they can be. All of this requires that you have a clear picture of how you'll measure success. This is determined largely by the kinds of customers & prospects to be found at that particular show.
Part of the problem we've seen is that marketing departments have great plans for the event, put together great booths & marketing materials, but they never communicate with the sales team. The sales folks who end up on the floor are dragged there kicking & screaming because they don't know what's in it for them. Remove the silo mentality on the front end and the results should markedly improve - as long as everyone's singing from the same song sheet.
It's pretty simple really - know what you want to get out of it, have a compelling reason to see those you choose to see, and maintain the discipline afterward to call, meet, email, and otherwise build relationships with those that are worthwhile. Spend $1.49 on a rubber doorstop - you're spend to attend that trade show is huge in comparison - don't waste it.