I participated in the "Best Practices in Trade Show Marketing" webinar sponsored by HR Marketer.com - if you do not get their newsletters they provide some pretty good information so sign up - I provided a link to their website below. Here is what I took away from this event:

Pre-show Planning

1.  Start 5 months ahead of time
2.  Be mindful of deadlines
3.  Look for early bird specials
4.  Make travel plans early to get good rates
5.  Determine WHO will attend and make sure they WANT to go
6.  Start promoting your presence at the show
7.  Ask for a press list

Planning for your booth

1.  Make sure it is welcoming
2.  Ensure that you have some strong messaging and graphics to say WHO you are, WHAT you do, and HOW you can help

Booth Staff

1.  Make sure everyone understands the goals and objectives of the show
2.  Prepare some engaging questions for them
3.  Give them a schedule with breaks

http://www.hrmarketer.com