My BFF Lisa Barone wrote a really great post about what companies should look for when hiring in-house SEO consultants. SEO folks should have some sort of technical skills and a little coding expertise too. They also should have an analytical mindset and be willing to stare at a lot of numbers. Other highly-regarded characteristics include the ability to research well, someone who can think outside the box, someone with a sense of ethics, and an individual who can grow within your organization.
Of course, there are other characteristics. You want someone with a passion for this line of work. If they're not interested, they may not be hanging on for a long time.
You'll also wan someone to be on top of their ballgame. Just like a programming language has updates and you'll have to learn new tips and tricks in order to stay ahead, SEO isn't much different. Things change. Algorithms shift. You'll need to be able to work on new strategies if you encounter something different, and the old tricks may not suffice.
Forum discussion continues at Sphinn.