Recruiting.com

Two Surefire ways to check technical skills of your candidates.

1) Check Technical references (Supervisors). 

The point of a reference is not, as is generally assumed, to find out ifyour candidate is a good guy or gal.  Only an idiot would give references of people who would not put in a good word for them.  Thus the reference check is useful in screening out idiots, but not so much for determining technical availability.

The key for determining skill lies in questions about the reference, not the candidate.  I interview the reference, trying to determine if they are technically apt, helpful, and willing to talk about specific situations that will match up with comments the candidate has made.  Asking if they work well with people is just a round about way of trying to get the reference to make a mistake and admit your candidate is a dud.  The far smarter way of approaching this is asking the reference how they helped the candidate learn, grow, and achieve.

After all, a reference should be a supervisor, and if the supervisor is a brilliant and patient teacher, chances are you've lucked out with a well-taught candidate.  If the supervisor is non-technical, but ran the department, where did the candidate go when they were stuck? 

Finally, if the conversation has gone well, don't forget to ask the reference for referrals, other references for the candidate, and even business or the possibility of the supervisor switching positions (not necessarily in that order).  A good reference check is business development, and as we all know, we're all responsible for business development.

2) The second way to check a technical reference is the "Tell Me" method.  Far too many recruiters like to hear themselves talk, so they don't give the candidate time to tell their story.  The Tell Me Method starts with a brief explanation of the company and the position, followed by the statement, "From the information I have given you, please tell me what you think the position is, how your skills apply, and why your technical expertise will convince your new boss to hire you.

This method is all about listening and giving the candidate the chance to shine.  Organized, disciplined minds respond well to this kind of questioning.  So do conceptual thinkers.  Both of those types of employees are valuable, and tend to ask more questions to clarify the position.  Poor performers, and the chronically discontent can't answer without giving themselves away.  They are looking to please you in order to get the job (deception and inertia are how they maintain their current jobs), so asking them to talk without clear direction will tell you all you need to know.

Picture taken from Dave at Dr. Fun's website. .