Here is an excerpt from my first article;
What you should know about choosing a web site design company to ensure that your website will be as good as it can be.
Look at Previous Designs
Most web designers or design companies will have a portfolio of websites that they have worked on and these are usually available on their website. Take a moment to browse through these looking for diversity and quality. The number of sites they have worked on is also a good indicator of longevity in the industry.
How Stable and Reliable is the Company?
You want a web professional that will see the job to the end and not leave you with a half finished website. I have seen a number of clients come to me requesting that we take over their website because the designer is no longer with the company or has gone into another line of business.
Also, always ensure that your domain name is registered directly in your companies name and that the website hosting agreement is with your company. Trying to takeover these accounts from a designer who has moved on can be near impossible.
What is the Company's Reputation?
Look for testimonials from existing clients on their website, and if they don’t have testimonials on their website ask them to refer you to customers that will be willing to talk about their experience with the designers. Google their company name and look for customer complaints.
You can read the rest if this article at http://www.firsttech.net/Website_Design/Website_Advice/jit_default_951.How_to_choose_a_web_site_designer.html
If you find this information helpful, please link to the original article on the FirstNet website