I haven't had to do it very often, but I have told people that interviewing someone for a job is almost as nerve racking as being interviewed. This article I came across on BNet has some very useful tips...
10 Mistakes Managers Make During Job Interviews
by BNET Staff
Hiring is one of the hardest parts of managing a team. A lot is riding on the initial meeting, and if you're nervous or ill-prepared—or both—it can make you do strange things. The following mistakes are all too common, but they're easy to avoid with some advance preparation.
1. You Talk Too Much
When giving company background, watch out for the tendency to prattle on about your own job, personal feelings about the company, or life story. At the end of the conversation, you'll be aflutter with self-satisfaction, and you'll see the candidate in a rosy light—but you still won't know anything about her ability to do the job.
2. You Gossip or Swap War Stories
Curb your desire to ask for dirt on the candidate's current employer or trash talk other people in the industry. Not only does it cast a bad light on you and your company, but it's a waste of time.
3. You're Afraid to Ask Tough Questions
Interviews are awkward for everyone, and it's easy to over-empathize with a nervous candidate. It's also common to throw softball questions at someone whom you like or who makes you feel comfortable. You're better off asking everyone the same set of challenging questions—you might be surprised what they reveal. Often a Nervous Nellie will spring to life when given the chance to solve a problem or elaborate on a past success.
4. You Fall Prey to the Halo Effect (or the Horns Effect)
If a candidate arrives dressed to kill, gives a firm handshake, and answers the first question perfectly, you might be tempted to check the imaginary "Hired!" box in your mind. But make sure you pay attention to all his answers, and don't be swayed by a first impression. Ditto for the reverse: the mumbler with the tattoos might have super powers that go undetected at first glance.
5. You Ask Leading Questions
Watch out for questions that telegraph to the applicant the answer you're looking for. You won't get honest responses from questions like, "You are familiar with Excel macros, aren't you?"
6. You Invade Their Privacy
First of all, it's illegal to delve too deeply into personal or lifestyle details. Secondly, it doesn't help you find the best person for the job. Nix all questions about home life ("Do you have children?" "Do you think you'd quit if you got married?"), gender bias or sexual preference ("Do you get along well with other men?"), ethnic background ("That's an unusual name, what nationality are you?"), age ("What year did you graduate from high school?"), and financials ("Do you own your home?")
7. You Stress the Candidate Out
Some interviewers use high-pressure techniques designed to trap or fluster the applicant. While you do want to know how a candidate performs in a pinch, it's almost impossible to recreate the same type of stressors that an employee will encounter in the workplace. Moreover, if you do hire the person, they may not trust you because you launched the relationship on a rocky foundation.
8. You Cut It Short
A series of interviews can eat up your whole day, so it's tempting to keep them brief. But a quick meeting just doesn't give you enough time to gauge a candidate's responses and behavior. Judging candidates is nuanced work, and it relies on tracking lots of subtle inputs. An interview that runs 45 minutes to an hour increases your chances of getting a meaningful sample.
9. You Gravitate Toward the Center
If everyone you talk to feels like a "maybe," that probably means you aren't getting enough useful information—or you're not assessing candidates honestly enough. Most "maybes" are really "no, thank yous." (Face it: He or she didn't knock your socks off.) Likewise, if you think the person might be good for some role at some point in the future, then they're really a "no."
10. You Rate Candidates Against Each Other
A mediocre candidate looks like a superstar when he follows a dud, but that doesn't mean he's the best person for the job. The person who comes in tomorrow may smoke both of them, but you won't be able to tell if you rated Mr. Mediocre too highly in your notes. Evaluate each applicant on your established criteria—don't grade on a curve.