Generally you need to save the receipt you received at the time of purchase if you want to return an item, and sometimes stores require that price tags or stickers are still on the purchase. Instead of refunds, some stores offer store credit with which you can buy something else there for the same price. Stores also post what kind of payment they will accept. All stores will accept cash, but not all accept credit cards or personal checks. If you want to pay by check, make sure you have with you the appropriate identification documents required by the store.
Stores also have different security policies.
Some will require you to leave any shopping bags at the front of the store. Others will insist on stapling your bag, even if you are leaving the store immediately. Sometimes stores have video cameras or large mirrors to defend against people who steal from stores, called shoplifters. If you are caught shoplifting, you could jeopardize your visa status.