(FORTUNE Magazine) – A female executive (let's call her Jane) desperately needed help: she had an encyclopedic knowledge of her industry, thought quickly on her feet, but was a lousy manager. Among her deficiencies: she took on all critical projects single-handedly and simply didn't communicate with her staff, rarely responding to voice mail or giving guidance on their work.

Enter the executive coach. At vast expense (coaches run as high as $2,500 per day), her company hired one for her. Using confidential written feedback from Jane's staff, peers, and boss (called 360-degree feedback in the parlance of the industry), the coach held a series of one-on- one sessions with her to identify the management skills she lacked and to develop a plan to build them. Slowly, Jane's behavior began to change: she actually started handing out compliments and delegating work.

Six months later Jane was promoted (partly in recognition of improved management skills), and to her company's dismay, she promptly reverted to her lone-wolf management style.

Jane's experience is not unusual, says John Kotter, professor of leaders hip at Harvard business school. His explanation: "She got three months of coaching--but she's not 10 years old--it's too much to hope for that she would change radically."

So coaching, yet another management fad, bites the dust, right? Wrong. In the past year alone, membership in the International Coaching Federation, an industry trade group, has doubled to 2,600. In 1996, enrollment at Coach University, an organization that teaches coaching skills, grew from 285 to 785. Coaches are in demand. The trick, though, is knowing how to use them.

These corporate cheerleaders come in a variety of flavors, but three are most common: executive coaches who help modify your behavior on the job (a la Jane), life coaches who help you set business and personal goals, and organizational coaches who help you get your life in order.

At its best, coaching is clearly superior to training. It is far more time efficient, and it is tailored to individual needs. But before hiring a coach, consider the following:

Are you open to changing? "The fundamental challenge in coaching is to get the individual to relax, open up, and really think about his leadership style in a profound way, without being defensive or looking for arrows," explains Kotter. Leocadia Burke, senior consultant at the Levinson Institute, a Boston executive development firm, concurs: "The No. 1 reason coaching fails is that people don't accept accountability for their behavior." Ask yourself if you are ready to accept potentially difficult feedback and whether you really want to change. (Be honest: Do you want to involve your subordinates in more of your decisions? Get to meetings on time? Be less confrontational with peers?)

Are you realistic about what coaching can do? "Beware of any guarantees," counsels Michael Shahnasarian, president of the National Career Development Association. And don't believe coaches who claim to have catapulted their clients to much higher positions and income levels. "There are so many variables leading to promotions and increased sales, it's hard to say that it was the coaching that made you more money," says Burke.

Do you have achievable goals? Wendy Wallbridge, a coach based in Larkspur, California, warns clients not to set aggressive and potentially conflicting goals. For example, don't pursue a tough business target, like doubling your company's size in a year, and at the same time try to shed 20 pounds. If achieving all your goals at once seems impossible, it probably is.

Are you prepared to work--hard? Quite simply, you get out of coaching only what you put into it. Says James Flaherty, head of New Ventures West, a San Francisco firm that trains coaches: "It's like hiring a personal trainer. To get in shape, you still need to lift the weights and sweat."

Well, if you are now overwhelmed by the idea of working with a coach, here is some good news: it is very possible that you don't need one. "Sometimes bosses are skilled people. They don't need outside help to coach their staffs. There are more of those than not," says Burke. Kotter agrees: "The best coach is a person's boss." So before you call a coach, look in the corner office and see if the boss might qualify.