Old experience: You need not tell what you did two decades ago. If you did something amazing, keep it otherwise no. Focus on the recent decade of your experience highlighting a few accomplishments. Is the role you held two decades ago still relevant today? If yes, then keep it.
Too much: Don't pack your resume with too much of experience. Recruiters and hiring managers are interested in candidates with the right amount of experience. Giving anything other than relevant experience will reduce your chances of getting the job.
Unrelated jobs: If you have got enough experience, you can omit the mention of your part-time job of your college days or a job in unrelated industry. If you include everything you did over a span of 20 years, your resume becomes a messy document that can confuse recruiters.
Short-term jobs: A short-term job shouldn't be in your resume. For example, if you are applying for a sales manager's post, you need not speak about your three-month stint as sales representative somewhere. A short-term job can be mentioned if that is the only proof of your industry experience.
Internships: At the beginning of your career, internships are a must. When you have gained experience, don't bother about internships. Give employment history.
Different versions: You should not make the same omissions for every position. You should see whether the experience you use is relevant to that specific job. Read the job posting carefully and highlight the experience that meets the job requirements. So you must have different resumes for different jobs.
Experience in a nutshell: Confused as to how to highlight your recent experience in your resume? Give more of your recent experience. Speak less about older jobs.
When you prepare your resume, reassess the applicability of your experience to a particular post. As a resume should be of one or two pages, keep only the most essential parts of experience.
