If you’re over 55 and job hunting, you already know it’s tough out there. Unemployed older workers are spending far longer looking for work than their younger counterparts. The latest data from the Labor Department shows that laid-off workers 55 and older spent an average of 35 weeks looking for work, compared with 30 weeks for 25 to 54 year-olds.

One reason experts say older professionals are having trouble: age bias on the part of employers. Roughly 25% of employers said they were reluctant to hire older workers, according to a 2006 survey by the Center on Aging and Work at Boston College. A 2007 study by the National Bureau of Economic Research found that after looking at only a resume, employers discriminated against women they perceived to be 50 or older. Job seekers and career experts say the trend has become worse since the recession began.

To combat age discrimination — an incident in which a job applicant or employee is treated less favorably in any realm of employment (from hiring all the way to job termination) because of their age — older professionals need to “come up with a plan to change the employer’s focus,” says Phil Rosenberg, president of reCareered, a career coaching service and web site. The biases potential employers might have include a belief that older workers aren’t tech-savvy, have lower energy levels, demand too much money, or are harder to train than younger workers. And then there are the subtle biases that wouldn’t stand up in court but still hurt, like the oft-heard term about experienced professionals interviewing for jobs: overqualified.

Here are four ways to turn recruiter perception around during the hiring process – and before it starts.

Revise your resume

By altering the emphasis and structure of a resume, job seekers can shift the focus from their age to their experience, achievements and skills, says Sherri Thomas, founder of Career Coaching 360. Highlight achievements in a measurable way: List the percentage increase in revenue that your department achieved under your watch, for example. This signals to employers that you are results-driven and motivated.

Also, listing every job isn’t mandatory. “It is fine to limit what experience you include on your resume,” certified career coach Hallie Crawford says. When applying to managerial jobs, list the past 15 years of experience, 10 years for a job that requires a fair amount of technical skill and five years for a very high-tech job. This takes emphasis away from your age and can also help combat the “overqualified” stereotype. Most employers are wise to the trick of leaving college graduation dates off a resume, says Crawford, so don’t do it. And don’t leave experience dates off either. But, it’s ok to, say, put that education line all the way down at the bottom of the document.