It's a question we'd all have a different answer for. Bottom line is that whoever you get, the site should be user friendly, secure, and have a shopping cart.

Above all though is Search Engine Optimization. You can have the best site in the world but if nobody sees it, because the search engines aren't aware of it, it won't matter how good it is.

I'd say before you make any decisions on developing a website you learn all you can about SEO...it's a science unto itself.
Good luck
Denny