When you're in the hiring phase for an SEO expert, you should get to know a little about the potential candidate you're considering by asking the right questions. The SEOpranos blog has 10 questions that should be asked at every interview. One of them in particular resounds well for webmasters:
Can you tear this website apart?
Chance are, if they don't find anything wrong with the site, they're not ready for "SEO expert" work. That's not to say they can't be trained, but they're beginners, not experts.
Other questions include asking what types of blogs they read, how would they go about building links, how they track results to prove success, and others.
While some folks have trouble believing that the list is accurate at Sphinn, a good number of Sphinners believe it to be very useful. And if you're not an SEO expert, it definitely provides advice on how to hone your craft. You can't really go wrong with having some knowledge of these questions and their answers.
Forum discussion continues at Sphinn.