How you handle early job experience on your resume depends on its relevance to the job for which you are applying. The more relevant the experience, even from years ago, the more likely you want to highlight it. Conversely, the less relevant, the more you will want to consider omitting or shortening the job entries. Combining early job experience can be done in a variety of ways, depending on your individual situation.
One Employer, Multiple Jobs
A person sometimes "rose through the ranks" at a job, perhaps starting right out of school in an entry-level position, but eventually becoming a manager. While this can emphasize the fact that you were promoted repeatedly, it can also consume a lot of space if you list each job on a separate line. If this is your situation, you can summarize the earliest jobs with a lead-in like "Early Positions" and a colon before listing the various titles. You can then give a date range that covers all of the jobs. For example, if you worked as a clerk from May 2008 to August 2008; a sales associate from September 2008 to June 2009, then a senior associate from July 2009 to February 2010, you could list the jobs as: "Early Positions: Clerk, Sales Associate and Senior Associate - May 2008 to February 2010."
More Distinctive Than Relevant
Some early jobs may not be particularly relevant to your current career, but may include duties you do not want to omit from your resume. For instance, you may have been a manager at a fast-food restaurant in college -- and while that may not mean much in your IT career -- you want to show that you have management experience. If this is the case, you can include a summary section of "Early Career Experience." For example, you could cite "Early Career Experience: Managed a crew of as many as 15 people for multiple companies in the fast-food industry" without detailing each position you held at McDonald's in high school and Burger King in college.
Sometimes early job experience is completely unrelated to the position you are seeking, but you do not want to leave years of your career off of your resume. Often, after a layoff or career path change, you will find yourself with a tremendous amount of experience that does not have a tie to your current career. On the other hand, you may want to either show that you are an experienced member of the workforce, with the wisdom that implies, or avoid showing that you have so much "time served" if you are worried about being passed over for a younger candidate. In these cases, a summary section of "Additional Experience" can cover years of work in a sentence or handful of lines. You can include the dates to emphasize your experience, or omit them to de-emphasize it.
Don't Overdo It
The important thing about early job experience is not to include too much. Certainly, select jobs or duties may be relevant, or even provide talking points for an interview (did some grunt work on a major motion picture or for a professional sports team?). But no employer seeking a full-time employee needs to know every single job you've ever held, including those part-time and summer gigs from your teenage years. Giving equal space to old positions takes up valuable room, and going back years and years to your earliest work could even put you at risk for ageism.