Some businesses offer credit-only which forces you to buy from them exclusively. Look for testimonies from past customers. Read what other people are saying about the company. Sometimes you can contact past customers and ask for their opinions personally. There's no better way to turn a customer off than with terrible customer service.
Customer service is the backbone of all businesses.
Ask the customer service department a question and note how long it takes for them to answer you. This will give you an indication of how long it will take for them to get back to you if you had a problem with a product. Autoresponders in my book are not personalized service although some businesses can use them very effectively. There's no way of telling the quality of the merchandise by looking at a picture on the internet, but sometimes you can tell by the way it is priced. Although a sale or discount is great, sometimes products are reduced so low it is ridiculous.