My mother, age 90, recently decided to change doctors. Her reason: The new doctor takes care of two of her friends and both say, "He listens to you and takes his time."

But first, my mother told me, "I'm going to see him and find out whether he'll take me and whether I like him."

Don't be shy, say doctors themselves, about making a get-acquainted visit or subjecting a doctor to this kind of scrutiny. "You may be playing Russian roulette with your health, perhaps even your life, unless you know how to check up on your doctor" and the entire health system, write Dr. Morris Placere and Charles Marwick in their useful book, "How You Can Get Better Care for Less Money" (Walker).

Your check-up can start when you phone for an appointment. This is the chance to ask a few revealing questions.

Such as, what's the usual fee for a routine office visit? And for a first visit with a physical exam? Most doctors and their staffs will discuss fees in these cost-conscious days. If a doctor won't, says Dr. James Sammons, American Medical Association executive vice president, it shows "insensitivity to a very serious concern."

Ask for a thorough physical if you can afford it or your insurance will help cover it (which it should if you have a complaint that requires investigation). If you're entirely well, an introductory physical will still give the doctor base lines to judge you in future.

You may need to know whether a doctor takes Medicare or Medicaid patients, or if you'll be asked to pay cash. Some doctors now ask for payment at every visit; some ask it of new patients. But most will discuss the matter and many will agree to another plan if you can't pay immediately.

You might ask whether the doctor is usually able to keep appointments. Most of us want a doctor who comes reasonably close to keeping on schedule, although a busy doctor who makes room for emergencies is sure to fall behind at times.

If you're going to have a long wait, the doctor's staff should warn you and tell you why. A courteous, helpful staff usually reflects the doctor's own personality. Beware of chilly or hostile assistants or grudging answers to a few telephoned questions, unless you're calling at an overly-busy time -- in which case the assistant should ask, "May I call you back?"

When you see the doctor, ask a few more questions: "What do I do if you're out of town?" "Can I ask you a question on the phone occasionally?" But don't come armed with a voluminous list or ask so many questions that almost any doctor will be antagonized. Just a few answers should tell you whether or not this is a concerned physician.

The way the doctor examines you may tell you more than any question. A thorough exam should include questions about you and your family, job, finances or other problems, your emotional as well as physical health. Your doctor should get to know you.

Most doctors agree that no doctor can take an initial history and do a thorough physical in less than 30 minutes, and that's fast. Many take an hour.

Two tests:

If you said you wanted a thorough physical or you have a serious problem, and the doctor does not have you take off all your clothes and examine you from top to toe, you have not had a thorough physical.

If you leave feeling that you have not really been examined -- you weren't probed in significant places or you didn't have a chance to say something significant -- you were probably slighted.

Other points to look for:

* Does the doctor do a health risk appraisal, asking about smoking, drinking, eating and exercise habits?

* Does the doctor explain things in a way you can understand? Most good doctors like to explain and teach -- the very word "doctor" comes from the Latin "to teach."

* Do you like the doctor? Not every doctor can have a great personality. One of the Washington area's best surgeons, commonly used by doctors and their families, has a notoriously cold manner. But he knows what he's doing when he gets to the operating table.

Still, your personal physician should be able to reach and inspire you, to make you feel concerned without being unduly apprehensive, to make you feel you can say whatever is on your mind and that you're in good hands.

As an internist told Medical Economics magazine: "Pick your doctor carefully and intelligently; choose him on the basis of training and ability; match your temperament to his; and don't let yourself be over-influenced by personality, bedside manner and other external factors."

What if you apply some of these tests and still are not satisfied? Shop around.

But what doctor will live up to them all? Probably none.

Don't expect perfection. If your doctor is sometimes humble enough to say, "I don't know," be thankful.

Coming Dec. 5: What else should you expect of a doctor?