Q: Some of my proudest accomplishments occurred at jobs that I had 20 years ago. A friend recently told me that I should not be going that far back on my resume.
A: Every situation is different, but – for the most part – you don't want to go back more than 10-15 years on your resume. This standard is very disappointing to a lot of people, especially since we tend to have strong emotions associated with early-career accomplishments. Remember, though, that it's best to keep your resume as succinct as possible. You want the potential employer to learn all of the details of your background and experience via an interview. Plus, sticking to your most recent experience helps in warding off discrimination, etc.
Don't be afraid to allow older and less relevant position to age off of your resume. If you really want an employer to see that position from 20 years ago, send them to LinkedIn.