How to select a Professional Web Designer

Professional web design companies seem almost outnumbered these days. The market is flooded by freelancers, "garage" companies and Johnny next door, all offering a solution to your web design problems. Many of these smaller companies, on the face of it, offer very competitive rates and may even sound very professional, using the right web related jargon like "search engine optimization", "e-commerce" and "meta tags"! They do seem to have all the answers, don’t they?