When you first make a call to the consultant ask these basic questions
Greet them first, ask them is it the right time to call them

• current location:
• Is he/she open for relocation:
• Whats his/her Work Authorization:
• When did they come to USA first:
• On which visa did they come to USA:
• Total Experience:
• Total USA Experience:
• Availability:
• What is the best time to reach you:
• SSN# (Last 4 digits):
• Alternative Ph#:

Then as per skill matrix ask consultant whether he/she has
Experience in those skills
How many years Experience in each and every skill
When was the last time they used those skills
Then ask them some questions on the skills they have been using
(use google to get some interview questions - example: .net interview questions)

About Exp:

Tell me about your recent project
What are the challenges you faced/came across in this project and how did you over come them.
While consultant giving answers observe their comm skills,
any hesitation, not clear in explaining or expressing, attitude
these things you should be aware off - if you are not satisfied even for a bit then the sucess rate off this consultant in clearing the interview goes down.