When interviewing potential job candidates, one of the major errors many entrepreneurs make is that they don't know what they're looking for. Nice looking? Well dressed? Tall? Physically fit? These factors are easy to identify and clearly impact the outcome of an interview, but they're not indicators of success on the job-unless you're looking for a model.

So what can entrepreneurs do to help ensure they hire the right candidate for the job? The best answer is: Know what you're looking for. If you don't know what specific characteristics the best candidate should have, then you probably won't find the right person for the job. The result? An inappropriate hire.

Even before looking at your first resume, you need to consider several factors. First, identify the specific and measurable knowledge bases, skills and abilities the available job requires. Hopefully, you'll be able to find this information in the job description. (If you don't have an existing description for the job that's available, this article by our Legal Columnist Chris Kelleher can help you get started.)

As you review it or create it, the key here is to be very specific about what you want. For example, a "good or working knowledge of Microsoft Excel" is not sufficient to differentiate an intermediate from an experienced person. Being specific, and measurable, you could say, "Using Excel, able to add, subtract, multiply and divide figures, create multi-colored bar and pie charts, sort and filter data, etc."

Second, make sure you ask behavioral questions, those that ask for specific, action-oriented responses, instead of vague, abstractions. For instance, if you ask someone if she is successful or not, you'll probably get a "yes" or "no" reply that doesn't really provide any concrete details. However, if you also ask, "And could you give me an example of a particular project of yours that you completed successfully?" you then have a response that will provide you with concrete, insightful information.

Third, check out your applicant's nonverbal behavior. If the candidate sits rigidly without moving, if he or she doesn't make or keep eye contact with you, or if he or she is turned away from you, these are clues that this person is uptight and not interested or able to engage you in relationship building. On the other hand, if the candidate is nervous, frequently changes position and gestures in a bothersome manner, then that person is probably just anxious or worried about something. What does the candidate's posture tell you? Is it slumped down or forward, looking lazy or tired? Rigid and nailed to the chair? Look for behaviors that express life, interest and enthusiasm without appearing too manic or too subdued.

In addition, evaluate the candidate's verbal behavior. Is their tone of voice loud or soft, appropriate or inappropriate to the situation? How about the types of words they use? Are they simple, simplistic, or complex and complicated? What is the pace of their speech? Is it too slow or too fast? As in all these examples, a medium level of verbal behaviors is usually most appropriate; other levels might help you screen out the competition.

Finally, after assessing these important factors during the interview process, identify and assess the residual feelings you have both in your head and in your gut. Do you have some gnawing feeling that something may not be "right" or "good?" Were you "blown away" or "under impressed" with what the candidate said or did? Whatever you experience during or after an interview, make certain you probe your reactions to uncover your true feelings. As a result, you'll be developing more confidence in your interview skills and discovering more concrete, helpful information to help you make an effective hiring decision.