Another tip is to organize your résumé chronologically so it's easy to follow.If your most relevant accomplishments are not your most recent, start the document with a Career Highlights section and place your greatest hits there, Scarborough Civitelli suggests.If, like Mann, you haven't updated your résumé in at least five years and aren't sure where to start, consider this your primer.Just because you've been in the workforce three or more decades doesn't mean you should list every single job you've had.

"Human resources professionals and recruiters are trained to look for gaps, and that's the first thing they're going to ask about," says career coach Sherri Edwards, owner and principal of the Seattle-based consultancy Resource Maximizer.

Online services like Jobscan can tell you how well your résumé aligns with a particular job description.

Scarborough Civitelli warns against gaming the system by stuffing your curriculum vitae with keywords or sneaking them in using white text.

For Mann, polishing his résumé for the first time in two decades was almost as daunting as having to find a new position.

"My résumé was in terrible shape," says Mann, of Bellevue, Wash., who was laid off in 2009 and is now 65.