so, just as you'll be expecting from the sales guy, go in w/ an open mind.
let him know within the first couple of minutes what you want, and then see what else he suggests.
there are probably plenty of bikes that will make you happy, humor him and ride around the parking lot on all of them.
if they are trying to push to in one direction that you're not sure of, walk away. go home for a few hours and think about the whole experience.
maybe after a little while you'll understand what the sales guy was getting at, maybe even agree w/him. Maybe not, maybe you'll be angry. one thing for sure though, you'll be more angry if you buy a bike you didnt really want.
You're the end user, the boss, the guy w/the cash. you're not doing this guy a favor by coming into his shop, you dont owe him anything. dont try to make him happy.