I'm far from an expert, but I've interviewed some people,
and use the simple same method which worked quite well for me :

I try to make the candidat comfortable/confident, make him talk a lot,
and try to only seek/look for the good sides, I'm not filtering the "bad", I'm chasing the "good".

It's not just rethoric, or "over-kind" attitude let me rationalize this to all of you who think that buziness is buziness
and that we only have to find to right person for the job, not be 'kind' in anyway.

• I make him talk, to avoid the question/answer scheme which stress a lot of people
  (they feel it as an exam and it reduces their efficiency)
  furthermore the more they talk the more I learn about them.
• Being kind, make them more confident the shy one will be more efficient,
  the sneaky one will lower his guard, the average guy will just have a more pleasant interview
• I avoid direct precise questions to avoid the 'exam stress' and beccause anyway you learn more (IMHO)
  through open questions than trough precise (closed) questions.
  Moreover I don't judge people on what I know that they don't know but rather on what they know that I don't.
  
• When you 'chase the "good"' you tend to ignore less people potential
  (which is more important FOR ME than current experience/skill).
  Anyway each coin has two side :
  Creative people tends to be less organized.
  Specialized poeple adapt slowly than genralized one.
  You got the Idea...
  It's may be a cultural point of view, as you (american people) seems to estimate people more on their current skills,
  but I tend to estimate people on their potential/personality and then try to see how I could exploit their strengths.
  You may say that sometimes you're looking for the 'right person' to do a 'well defined job' and you can't afford to teach the newcomer.
  But any 'newcomer' has to adapt to the way of working in the company, learning new skills is often not so expensive...
  

Let me give some examples :

I know linux.
Q: What distro do/did you use ? what do you enjoy most with this distro ?

I know SQL/Databases.
Q: What is your favourite database and WHY ?
Or if he only uses/knows one : What is your favourite feature, what is the one missing to your mind ?

Even for those who stay elusive, you can learn a lot without 'examining' them :
I've written CGI scripts for just about every site in my resume.
Q: Which one is your favourite ? The one which makes you feel proud. can you tell me more about it ?

As you see, I ask them to speak about what they say they know,
and then try to estimate their answer based on what I know, and their way to answer.
It's not so difficult to check the veracity based on what you know.
Often simple details that match your personnal experience are enough :
'mod_perl just run fine, I just got bitten once with a script using __DATA__'
'The custom server install was a little buggy, especially with the network settings'
'It took me sometimes, before I remembered the BYPASS_DBA_AUTHORIZATION modif to do in the registry'...

"Only Bad Coders Code Badly In Perl" (OBC2BIP)