Many entrepreneurs I meet—even mom-and-pops and SOHOs—spend thousands of dollars on hiring so-called experts to advise them on how to make their businesses more successful.

Sometimes, the expert’s advice works out, the investment is recouped, and the entrepreneur is better off for consulting with a professional.

Other times, the expert’s advice is either useless or wrong. The client has thrown thousands of dollars he can’t afford to lose down the drain, and sees no improvement in his bottom line, productivity, efficiency, or operations.

Since I am frequently on both sides of the table—I sell my services as a copywriter and consultant, and also buy lots of services for my little Internet marketing business—I have a small bit of advice that might save you this agony…and enable you to select advisors who can actually help you.

In my experience, there are 3 types of experts for hire.

The first type of expert I call the teacher.

“Teachers” are those who give training, speeches, and seminars…write books and blogs and columns…sell their expertise as consultants or coaches—but don’t actually practice what they preach.

You know the expression “those who can, do; those who can’t, teach.”

I don’t think it’s always true…but these teachers have never, for the most part, proven that they can do what they talk about. They’ve only taught it or advised others how to do it, but have never done it themselves.

An example of a “teacher expert” is Tom Peters.

He is revered as a management guru, and writes endless books and gives speech after speech advising CEOs on how to be great managers and leaders.

But he has never been the chief executive of any company (running your own consulting business does not count).

The second type of expert is the practitioner.

This is someone who knows a particular skill or area because he does it—and does it successfully—rather than writes books or articles about it.

An example is Gary Bencivenga, who is arguably one of the greatest copywriters who ever lived.

Yet until his retirement, Gary—to the best of my knowledge—never wrote a book, article, or column on marketing. Nor was he a speaker at marketing conferences.

The third type of expert is the teacher/practitioner—an active practitioner who is also a writer, speaker, and teacher in his area of expertise.

A good example of this is Michael Masterson, who writes best-selling books on business success and entrepreneurship—based on his decades of experience building and growing many successful companies.

Some of the many companies he has been involved with generate annual sales ranging from $10 million to $100 million and beyond.

Now, as to which type of experts you should hire—and when…

If you are a seminar organizer or meeting planner, most of your speakers are probably teachers.

That’s because speaking is how they make their living, and so they are actively seeking these speaking engagements. And, they are good speakers.

The hidden truth is many practitioners for the most part shun speaking requests; they are too busy making money running their companies.

You may think hiring a professional speaker to give a professional speech makes sense.

After all, you want someone who knows the topic and can communicate it in a clear, motivating, and entertaining fashion.

The problem is that the teacher’s knowledge is all theoretical: gleaned from research and observation and thinking, but not actually doing.

Therefore, the teacher thinks he knows what works…but in reality, he is just making educated guesses.

MA, a professional speaker who also owned and operated several successful insurance agencies, once said that nobody should be a full-time speaker because if you are not practicing what you preach, you really don’t know what you are talking about.

Yes, you can hire a teacher as your seminar presenter or keynote speaker.

Many can deliver a rousing talk that gets a standing ovation and great evaluations.

But their expertise rarely extends beyond the content of the talk. And this shallowness inevitably comes through in both their presentation and their interaction with attendees after they step down from the platform.

If you are a small business owner hiring expert advisors and professionals—copywriters, strategists, consultants, and advisors—you should never hire pure teachers.

Think about it. Let’s say you want to hire someone to manage a pay-per-click ad campaign for your company.

Do you really want to take the advice from someone who has, over his lifetime, done fewer actual PPC ad campaigns than you have?

Someone who has merely written a book based on studying the PPC campaigns of others or real entrepreneurs with the guts to actually put their own money where their mouth is?

The bottom line?

Your key business advisors and vendors should all be practitioners or practitioner/teachers.

First and foremost, they should have long experience—and a terrific track record—in the discipline for which you seek their help.

For this purpose, either a practitioner or a practitioner/teacher will do nicely.

The one advantage of the practitioner/teacher over the practitioner is an enhanced ability to clearly and efficiently explain what he is doing…so his clients can learn and—over time—become more self sufficient.

I once heard the definition of an expert as someone who doesn’t necessarily know more than other people, but their information is better organized.

A practitioner expert, however, does know more than other people because he has learned from real-world trial and error.

A teaching expert, on the other hand, usually does not know more because his knowledge is gleaned from studying practitioners who do know more.

But the teacher’s information is better organized as a result of putting it into a seminar, workshop, or book.

As for the practitioner/teachers, they can in some instances give you the best of both worlds.

As their client, you get the expert’s in-depth experience and authoritative knowledge of the subject in which they advise you.

You also benefit from the expert’s ability to help you both understand what they are doing (and why) as well as educate you in their field.

That way, you can learn over time to do more and more on your own—if you are so inclined.

Bob Bly is the author of “World’s Best Copywriting Secrets” and has written copy for more than 100 companies including IBM, Boardroom, Medical Economics and AT&T. He is the author of more than 75 books and a columnist for Target Marketing, Early To Rise and The Writer. McGraw-Hill calls him “America’s top copywriter”.