Don't be afraid to ask questions. The music store can be a great place to learn. I learned a lot about used saxes the Summer I worked at a company called Wally's Music in Oregon City, Oregon. It was there where I learned the essentials of good sax repair and good business. They are always friendly and never consider a question too elemental.
Music stores can also be dangerous for buyers that are uninformed.
Music stores sometimes take advantage of the fact that they are businesses and fleece the unsuspecting or uninformed. Music stores are sometimes just as ignorant about saxophones as the uninformed buyer. This can either be good or bad, depending on if they charge more or less for their instruments. The more you know, the better equipped you are to do business with a music store. It is with some reservation that I bring up a pawn shop as a place to buy a saxophone.