I've been asked this question a number of times so here's my quick summary of things I’ve learned when hiring web designers:
- Figure out if they’re a real web designer or a graphic designer posing as one. Ask them how they make sure their designers are HTML-ready and SEO-friendly; if they stumble on that, you’ll know.
- Determine how involved you’ll be in driving the project. If you need a designer who’ll work via “mind meld,” you’ll need to find someone who can work without detailed specs and creative briefs. There are lots of good designers out there who operate this way, most of them have been freelancing or working at start-ups as most agency types get a lot of hand-holding.
- How technical will they need to be? If your site will be a static, information-based site and the designer just needs to hand over HTML-ready files, that’s pretty basic. But if you’re building a more complex site (eCommerce anyone?), they may need to be proficient in CSS and other technologies and communicate readily with your development team.
Finally, I found this blog posting recently called “How to talk to a web designer for dummies” which sums a lot up.