Should a lawyer, accountant or management consultant ring and wish his or her client a happy birthday? A group of professional services consultants at a seminar in Sydney recently spent 30 minutes discussing the pros and cons of the birthday wish, with half concluding it was completely inappropriate and the others supportive.

The discussion delighted U.S.-based writer and consultant Mr. David Maister, who was running the seminar and has written a book (with coauthors Mr. Charles Green and Mr. Robert Galford) called The Trusted Advisor.

His core message is simple: treat your clients as human beings, not as clients.

The whole issue of a birthday greeting takes on a different dimension when the client-adviser relationship is long-term and involves trust, Mr. Maister points out. While he did not advocate saying “happy birthday” to every client, the discussion helped crystallize some ingrained attitudes about the consulting relationship.

“There are large numbers of trained professionals who are completely uncomfortable with human beings,” says Mr. Maister. “And that’s exactly the point. Far from seeing their clients as human beings, they assume the greeting is insincere. But I also hate phony glad-handing. It’s not about applying one tactic to everybody.”

Treating clients as you would treat a friend is not only ethical but sensible business practice, and Mr. Maister visits Australia fairly regularly to deliver seminars to a bevy of professional consultants keen to hear this message.

In recent weeks nearly 300 people from professional consultancies in Australia have made up his audience. His style, according to participants, is confrontational and a little heavy on analogies with personal relationships. He claims the technique is needed to get the message “through their skulls.”

At heart, what he is saying is more about common sense than complicated theory, although actually applying the ideas is confronting for many. More patience, understanding and the ability to listen are keys, but this is a tough audience—driven professionals in cutthroat sectors, assessed on their billable hours and new business record.

And Mr. Maister even advocates—as a last resort—walking away from a client you really don’t like. There’s nothing wrong with that, he says. “Nothing in the book is anticommercial,” he says. “The issue is not, ‘Should we trade off against money or sacrifice revenue to this?’ What we are saying is you are more likely to earn a lot of revenues and fees if you take the time to build relationships.

“The best situation is to nurture the existing relationship, not the new prospect, but human instinct is hard-wired the other way. It’s about patience.” Mr. Maister knows this is not a one-way street—some clients are not loyal and treat consultants badly. And he has made every mistake he outlines in The Trusted Advisor, but maintains that taking the long-term approach does succeed in the end.

It’s not a lesson that is taught by business schools. After spending nearly 15 years at Harvard as an academic, Mr. Maister left the university with little idea of how to manage people. “After all my decades of business education I had no idea of managing. What is taught in the schools is analysis, not managing.” This is one of the reasons why Mr. Maister believes his message has fallen on receptive ears. “People are saying, ‘You’re right.’ There was a great hunger for this stuff.”

Aside from patience and trust, consultants must also be willing to take a risk and invest in the relationship. It involves pushing intelligent, ambitious people out of their comfort zones to deal with emotions and politics. “To a lot of people that sounds more risky than writing a proposal…and firms do unfortunately create all the wrong incentives. If you bring in a new client you get your name in the newsletter. But if you bring in more revenues from existing clients it’s not the same. There’s this macho environment.”

Some of the worst offenders are law firms. “They are incapable of change,” Mr. Maister says. “They do not understand the concept of a law. In any democracy there is broad consultation and extensive involvement, but in a law firm they say, ‘I’m a partner and I don’t vote for it.’ They are incapable of enforcing rules; although they have the right ideas, they can’t make it happen.” It’s a situation Mr. Maister believes will continue, although the move by the Big Five accountancy firms into legal services may force some change. The Big Five do manage, although badly, he adds. “I’m not a big fan of multidisciplinary firms, but they do have a concept of the first hurdle—attitude.”

The Trusted Advisor points out that there is a conflict between the people who succeed in the top firms—driven, rational high achievers who concentrate on their own performance—and the nurturing of trust. And the emotional side of the client-consultant relationship is a very difficult aspect for many professionals.

“It’s frustrating, but it is learnable. I tell [the audience] to think about how you would like the people who serve you to deal with you. I take them through what they hate about the way doctors deal with you and how you feel if you find someone who is the opposite of that.”

Most firms still believe people are the least important thing they have to look at.

“Don’t just manage the money; manage the things that make the money,” Mr. Maister says. “Professional service firms’ habits in terms of dealing with people are ridiculously ineffective if they want to make money.”