I would recommend listing all your experiences in reverse chronological order (most recent job at the top). For an entry-level position in the private sector, I recommend that you keep your resume to one page. If listing all of your work makes it go over a page, I would suggest trimming out the least relevant work experiences first, but maintaining a reverse chronological order. If you are applying for government work, it's recommended that you be more thorough in your resume, but I wouldn't exceed two pages (my government resume is two pages, after completing a BS in Software Engineering, ~21 months of employment in the field at various internships/co-ops, and a couple of TA and volunteer positions related to software development) for an entry level position.
My ultimate suggestion is very similar to Alan's comment. Write your resume in as much detail as you think is necessary. A lot of universities that I've seen have various career counseling services, so show them your resume and talk about it with them. They'll help you focus it down. But it helps starting out with too much and needing to trim it than trying to add more on the spot.