Try not to get too over-excited. Trust me, it’s very easy Also, sounds like the salesman actually gave you some good advice.
Pay close attention to everything in the class, ask questions if you don’t understand something. Chances are that you will be riding 250s in the class, so you should get a good feel for the power they can produce, and know if you want to go with a 250, something a little larger or something a little smaller.
Things to consider before choosing a bike: How will it be used? How tall can the seat be and still flat-foot at stops? Do you want a sport-bike (Ninja), or is a standard(TU250) or cruiser(Rebel) more what you are into? Do you like the look of a full fairing, half fairing or a naked bike (least important of the questions, but looks do matter)?
One more tip, when asking questions like this, it is best to post a new thread. That way you can keep better track of what people have said in response to your post.
Nate