10 Dos and Don'ts for Online Retail Startups

7. Don't fear the big boys. You have to be aware and somewhat paranoid of what the Amazon and Costco's of the world are doing, but you can't be fearful of them, Neblett said.

8. Don't overspend on customer acquisition. The lifetime value of your customers needs to measure up against what you're paying to get them, Neblett said. He cited companies that have worked with coupon sites such as Groupon failing because they've given up too much margin for customer acquisition — and in most cases, a one-time-only customer.