Front-End Web Dev Interview Questions

Hi, folks. I just found out that in roughly 26 hours, I'll have to interview someone for a job at my company. That is to say, I already have a job. We're hiring someone else to do more-or-less what I already do, which is JavaScript and AJAX web development. (I occasionally have to mess with HTML, CSS and images, but that's a secondary duty.)

I've tried a few Google searches involving words like "javascript" and "ajax" prepended to "interview questions" and gotten some pretty hideous results, so I thought I'd ask here: What do you think would be good questions to ask? What questions would you ask a prospective employee for such a position? Ideally, I want to be able to figure out:

1. Does this guy actually know his stuff, or has he padded his résumé?
   
2. What's his coding and architecture philosophy like? Aside from simply knowing JS, will he actually write good code, rather than some kludged-up mess?
   
3. Will he be good to work with?

I want to figure out the whole shebang, and that can certainly include asking him to write sample code, as far as I'm concerned. So, what would you all suggest for questions?

(Cross-posted to webdev.)