Find out about the features of the machine and try to determine how important that feature is to YOU.
By the time I decided to get a new machine, I had a pretty good idea what I liked, what I needed, and what would be nice. I also knew my price range. That set my stage. It is real easy to get caught up in the moment of the show. Take a reasonable (and supportive) friend if possible
When I bought my last machine, I negotiated the price. Dealers that gave me the "we barely make any money on this as is" got a (sym)pathetic smile and I walked away.