There are many great answers already, but I thought I will share a very common practice I have observed - specifically if you are hiring a contractor - be careful of a "substitute" scenario in phone interviews. Not everyone is using this trick, but if you are interviewing a substitute, then all of the suggestions from everyone else may not be of much help because the substitute might be an experienced techie who will be very comfortable with MOST of your questions.
EDIT: (per comment/suggestion from CMW)
I suggest that you...
- conduct interview over skype or facetime if possible. Irrespective of concerns of a "substitute", we should be conducting "phone interviews" this way. Phone interviews are to save on travel time and costs etc., not to keep face hidden from each other. Technology is available to us, lets make use of it.
- Check with your HR, but very likely you won't be allowed to ask candidate's age due to some regulations. If you figure that candidate is under 25, has masters degree and 7 years of experience on resume, a flag should be raised for further discovery. Not being able to ask age question has hurt me a few times but I now use following points to get to what I need to discover.
- During interview process, if necessary (use your judgement), inquire about the visa status / work authorization status of the candidate. Your goal is take some notes and connect dots to make sure whether this is a "substitute" OR if candidate resume is a falsified one. As a rule of thumb, for anyone with OPT or H1 status and less than 10 years of experience on resume, I engage in discussions about their education, university and when he/she obtained bachelors/masters degree etc. If nothing else, this will help you better understand your candidate.
First, note that this is not my opinion or a speculation, but reality as I have personally experienced and observed happening too frequently - sharing this info here for greater good. Significant number of resumes are "created to cater to your liking" - i.e. includes all of the made-up experience (borrowed from genuine resumes) to match experience levels you have asked for. Many times these candidates have ZERO years (yes, zero) experience with technologies you have asked for but resume will state experience in the range of 5 to 9 years! With H1 quotas for entire year getting filled in a week, one of the common practice I have observed that someone with 7 years of experience has NO REAL EXPERIENCE, is in early 20s, who came to US for a Masters degree (remember, no H1 quota?) and just finished the degree and is currently on a 29 month OPT work permit (H1 likely in process). The agencies paddling such resumes are typically Tier-II or Tier-III who work with Tier-I vendors (vendors approved by your company). Tier-I vendors are mostly clueless about what is happening and their technical recruiters are mostly non-technical.
Now you can easily spot someone who has no experience, can't you? That's when phone interviews come-in. Of course, phone interviews are an efficient way of filtering candidate pool, but in many instances a "substitute" with real experience takes that phone interview. If candidate gets selected, they get a payout of $500 or more for 30 to 60 minutes of their time.
These companies are betting on two things... once candidate is selected on a project, your organization won't even have a computer and user account / security etc. for him/her for couple of weeks. Also, candidate has done his/her best to make a "good impression" on a personal level during this time. By the time you as a hiring manager/architect figure out that you have been duped, 2/3/4 weeks of billable time has passed. Now, if you "fire" the resource from your team, "your bosses" are going to look down on you for your inability to select the right candidate in first place. If you have a large enough team, there is more than 50% chance that you will continue with this resource with assumption that not everyone is going to be a "superstar"!
Yes, this is anecdotal and I understand that not everyone will agree that this is happening, but I have seen it happening far too frequently. In our case (a Fortune 500 company), at least in one instance we discovered that the substitute was already a contractor in some other department of our company with in-depth knowledge of many of our processes and systems, and that he had give such interviews for multiple candidates who later became contractors within our company.
If this information helps someone, great! If not, please ignore it. If you work for a large company with many H1 contract developers, just look around within your existing contractors with an open mind and you might find 20% - 40% of them to match above characterization.
To add a little bit more credibility to my claim that this is happening far too frequently, I am adding a link here for curious minds - don't miss to read the comments section - http://h1bwiki.com/opt-student-deported-chicago-port-of-entry/ . If you are adventures enough, try using some "keywords" out of that discussion and google to find plenty more documented cases.
At end of the day, I remind myself that there will always be people who will do such things. My goal is to make sure I am not that sucker who falls for it, and to educate others when I have an opportunity to do so.