You've prepped for your big interview by lining up impressive answers about what you've done and can do, what's new in your field and in the company you're meeting with. But if you aren't tuned in to the three most common interview decision factors and their relative importance, then all your painstaking research, strategizing and rehearsing could easily come to naught.

The three factors are: Fit, passion and ability to do the job. Although that list is widely known, candidates often go wrong by emphasizing their ability to do the job. In an interview, that tends to be the least important of the three criteria. It makes up only 10 percent of the decision, says IT consultant Todd Zebert. The other two, fit and passion, together make up 90 percent, Zebert says on his blog.

"Fit" means how well a candidate is seen melding with the culture of the company, division and work group, as well as with the individual hiring manager (who in most cases will be the prospective employee's direct supervisor).

"Passion" is the degree of enthusiasm a candidate demonstrates (convincingly, of course) for the industry, company, and specific job.

"As a manager I interview for those first two," says Zebert, who has managed IT teams within a number of financial institutions, most recently ING.

What's Wrong With Ability? Nothing, But….

I remember hearing career coach Win Sheffield discuss the three interview decision factors in a lecture a few years ago. His formulation was: "Can he do the job? Does he want the job? Is he a fit?"

At that time, I was unemployed and in an active job search. Even though Sheffield mentioned "ability" first, his enumeration made me realize I'd been all but ignoring the other two factors in my interview presentations – thus hurting my own cause.

Whoa, you're thinking. Doesn't ability count? Sure it does. But hiring managers have several good reasons to de-emphasize it during interviews:

- To get even an initial interview, a candidate will already have submitted evidence of ability to do the job. Many who get as far as meeting a hiring manager will have done the very same job before, in a company similar to the one they're interviewing at.

- A candidate's ability to do the work can be gauged from a resume, work samples, pre-employment assignments or written tests. That lets interviewers concentrate on more subjective factors.

- A hiring manager might leave asking nuts-and-bolts questions about a candidate's qualifications or job-related knowledge to underlings or HR staff.

- Finally, all jobs require some adaptation, regardless of a new employee's past experience or knowledge base. "Given the constant changing nature of skills needed, and that we have 'our way,' the candidate will have a learning curve ahead of them anyway," notes Zebert.

The bottom line: When you meet the hiring manager, focus on demonstrating your alignment with the culture and your passion for the company and the role. Those are the issues most likely to make or break your candidacy.