It’s happened to many of us: We’re out and about and the cell phone rings, and an unfamiliar number pops up. Turns out it’s an HR official with one of the firms you applied to recently, and she wants to spend some time on the phone to learn more about you and your background. What now?

Take a few moments to explain you are in a public place and ask whether it’s possible to schedule another time to talk when it’s convenient for the both of you.

“One obvious tip is to be prepared,” advises Stephen Laser, Ph.D., a Chicago-based psychologist who is hired by financial services companies to interview and test job candidates before they’re hired. In other words, this is no time to wing it.

In an interview with eFinancialCareers, Laser says that usually what happens is that a member of the employer’s HR team will be sorting through your resume and will have questions they won’t be able to answer based on a quick read alone. For example, “Someone might say on their resume that they’re in institutional bond trading, and a question may arise as to why they have mostly public sector experience,” says the psychologist. “For someone in municipal bonds, the question might be, ‘How deep is your high-yield bond experience?'" The voice-to-voice interview can provide a level of depth and clarity employers just cannot derive from one’s resume alone.

Phone Interview Tips

To make sure you don’t blow your opportunity to meet with a hiring director face to face, here are some tips from Laser in conducting a phone interview:

• Don't wing it. Keep in mind this is not going to be a casual conversation—don’t think you can wing just it because you’re talking to the HR department and because the conversation happens to be taking place over the phone. Have your resume in front of you and in a format where you can read everything easily and clearly. You should not be sitting on the beach with your iPhone toggling between your e-mails and your interviewer. Try to be at a desk and your resume in front of you and be ready to devote 45 minutes to an hour to the call.

• Be brief. Remember that your interviewer may have spoken to half a dozen people or more on the very same day he or she has contacted you, so don’t go on and on when you’re asked a question. If the interviewer wants to know how long you’ve been in banking, for instance. Don’t launch into a ten-minute explanation detailing all the twists and turns your career has taken. Say you had your first job with XYZ Investments in 1995, and that you’ve been in banking ever since. When you get a follow-up question, answer that one as directly and briefly as you can as well.

• Watch your tone of voice. Be careful how you talk about your previous co-workers and supervisors. “Some people are very bitter” about work experiences that didn’t pan out, or where they were downsized, Laser observes. “Don’t vent on a former employer or boss,” he says. It’s unprofessional and will reflect poorly on you.

• Try to use a land-line. Assuming you are cold called, try and arrange a time to speak so the interviewer can have your full attention. If a cell phone is your only option, fine, but it won’t always be a clear connection so “If you can get to a land line, do it,” says Laser.

• Don't interview and drive. Don’t even think about driving while giving an interview. You want to devote your full attention to the call. Make sure you are in a quiet place without children crying or dogs barking.

• Examples of success. Be ready to give a couple of solid examples of success and achievement in your career. Some interviews “border on the psychological,” says Laser. What this means is that the person calling will want to hear about your achievements, what precise role you played in making them happen—and the lessons you learned along the way.