Make things convenience for the customer. It is there hard earn cash, make the experience easy and enjoyable. Do not consume the customer's time. If you want to lose a customer, go ahead and waste their time or make them wait. Today's customers hate to wait and would rather pay the extra dollar or whatever with the competition if they can deliver faster efficient pleasant service.
Consumers expect their shopping experience to be an enjoyable one.
If you can make it fun and entertaining to do business with you, chances are they'll be back and possible bring a friend or two. Don't be a General Practitioner. Find a unique angel to your business, be great at it and stick with it. This is called a Niche. You can have a Niche product, service or market.