I have presented for a number of years (4 coming up for me in Chicago....yikes!!) I agree with the others about checking the room ahead of time, being ready to set up on the fly, leaving a copy of the session in the business center for copying, etc. I would suggest having a place ready outside of the room to sell your poster's, etc as soon as yours ends. That way you won't interfere with the next session by folks gathering in the room.
What and when is your session?
creatively, Linda in Oregon