It’s easy in retrospect to say you would grab the leader who drove the creation of the iPhone, iPad and so many other things that built Apple into the most valuable company in the world.

But would you have taken on this scruffy college drop-out who showed some interest in technology but looked like a hippie and smelled so bad that Atari had to assign him to the night shift to placate co-workers who complained he seldom showered or used a deodorant? The negatives went beyond a lack of obvious qualifications, body odor and dress. He had shown himself to be, says Walter Isaacson in his best-selling biography of Jobs, manipulative and arrogant, and “a dreadful manager” who was not a great engineer and didn’t know much about technology.

Not many of us would have looked past these off-putting weaknesses to imagine his passion for perfection, an uncanny ability to understand the needs and desires of consumers, and uncompromisingly high standards. You might have hesitated, but Peter Drucker would have urged you to look again. Jobs is an instructive example of the management guru’s over-riding principle:

Hire people for their strengths, not their absence of weaknesses.

Avoiding weakness, Drucker explains in his classic The Effective Executive, will at best produce mediocrity.

Isaacson paints Jobs as a man of towering weaknesses … and towering strengths. A charismatic leader who inspired (and bullied) people to do more than they thought possible, he was one of those great business leaders without conventional credentials.

Another who lacked obvious credentials was David Ogilvy, the most famous advertising man in the world — and arguably the most important. But in 1949, he was 38 years old and had never worked in advertising other than a brief stint in his brother’s agency in London. He had dropped out of Oxford, and had worked as a chef in Paris, an oven salesman in Scotland, a researcher in Hollywood, a spy for British Security Coordination, and a farmer in the Amish country in Pennsylvania.

Many years later, Ogilvy sent a self-aware memo to his senior executives cataloging his lack of qualifications at the time:

Will Any Agency Hire This Man?

However, a London agency did hire him. Three years later he became the most famous copywriter in the world, and in due course built the tenth biggest agency in the world.

The moral: it sometimes pays an agency to be imaginative and unorthodox in hiring.

Another leader who took an unorthodox approach to hiring was Alan “Ace” Greenberg. Starting at Bear Stearns as a clerk, he rose to Chairman and transformed the firm into one of the most profitable investment banks in the world (before it imploded under his successors.) He showed his disdain for conventional credentials in a memo to his Partners.

There has been a lot of publicity lately about firms hiring students with MBA degrees. Our first desire is to promote from within. If somebody with an MBA applies for a job, we will certainly not hold it against them, but we are really looking for people with PSD* degrees. They built this firm and there are plenty of them around because our competition seems to be restricting themselves to MBA’s.

*PSD stands for poor, smart and a deep desire to be rich.

Identifying raw talent, without the benefit of conventional credentials, is elusive. For one thing, the “best” people don’t necessarily graduate from the “best” schools. Price Waterhouse (before it merged to become PricewaterhouseCoopers) conducted an analysis of where their top partners went to college. Turns out, it was not the “A” schools, as they classified them, but the B and C schools. (This did not spur a change in their hiring practices — too often, we want the confidence of the conventional.)

T. J. Rodgers, founder, president and CEO of Cypress Semiconductor, expressed his contrarian view on where and how to find skilled engineering talent. Not through Human Resources, although he valued their help in checking references. Rodgers expected his best executives to know the best people in their field, and recruit them for Cypress.

This is not to make a case for sweeping away proven guidelines for hiring. Only to emphasize that it occasionally makes sense to look beyond the check-list of conventional credentials, show some flexibility and take risks … and not to rule out candidates because they may be different. Most successful hires will come from proven sources with recognizable credentials. Still, it can pay to look past the resume … if you know what you’re looking for, and are prepared to invest time in some side paths of inquiry.

George Lois, a leader of the “creative revolution” on Madison Avenue, went to the Metropolitan Museum of Art every Sunday for decades for what he calls his “spiritual day of worship,” seeking ideas for his iconic advertising campaigns and Esquire covers. When he lectures at the School of Visual Arts, he asks “Who has visited the Metropolitan Museum this year?” The surprising few who raise their hands don’t know they have just made it past Lois’ first screen for creative talent.

In leading an advertising agency, I developed my own line of inquiry to detect whether applicants might be champions of advertising creativity as well as successful managers of client relationships. Instead of probing a candidate’s prior business experience (I assumed others had done that), I asked:

What was the last book you read? The last concert or art museum you visited? The last show or movie you saw? What magazines do you subscribe to?

Years later, I would meet people who remember these questions. Today I would probably ask what blogs they read. I was looking for their breadth of interests, their “feel” for a creative product, and their likely ability to work with copywriters, art directors and producers.

There is no perfect formula for hiring, conventional or otherwise. When Steve Jobs called for a brand image advertisement to articulate what made Apple different, it was directed not just at potential customers but also at what he hoped to find in Apple’s own employees.

Here’s to the crazy ones. The misfits. The rebels. The troublemakers. The round pegs in the square holes. The ones who see things differently. They’re not fond of rules. And they have no respect for the status quo. You can quote them, disagree with them, glorify them or vilify them. About the only thing you can’t do is ignore them. Because they change things. They push the human race forward. And while some may see them as the crazy ones, we see genius. Because the people who are crazy enough to think they can change the world are the ones who do.

Ogilvy, who regarded himself as an eccentric hire, put his copywriting talents to work in a full-page advertisement to recruit what he called Trumpeter Swans — “who combine personal genius with inspiring leadership.” The ad was a flop. Trumpeter Swans apparently don’t respond to Help Wanted ads.