If you're looking for an eCommerce development agency, you should seek one that specializes in the industry. You should also check about the developer profiles; will the firm assist once the website is launched? Do they have a set price structure or do they charge on a project-by-project basis, and how many hours do they charge? You want your new website developer to be as open as possible; if you think they're being evasive, look for someone who shares your values.