If you have a friend with mid/big grocery shop, I would highly recommend you to hang there often. If you have free day and can spare it there, Try it. you will learn tons of things from marketing, trading, negotiation, customer service, etc. (by the way my family owns a grocery shop, and I have also spent much of my free teen-age time at my uncle's grocery super-store which is kind of a mini wall-mart with 15000+ skus.)