I'm not at all surprised that most college-age kids don't know jack about buying suits. It seems most young people have little or no reason to dress up anymore. Most church-going people don't even dress up on sundays. People invited to a wedding may wear a button down with a tie, but that's not a suit. Many have never been to a job interview at an office where a suit would be appropriate.
If my father had not taken me to a suit store with tailors on hand to buy me my first real suit, I would have had no idea what to think about when buying a suit. I probably would have bought off the rack, tried it on real quick and maybe gotten the pants hemmed. That's why I strongly recommend going to a place where you can talk to knowledgable salespeople and/or a tailor to see what you should look for in buying a suit (e.g. the cut, fit, what to alter, etc.)
Buying a suit is similar to buying a car. It is something you have to learn how to do properly otherwise you get screwed.
