IMO, if it's a completely different position (not an increase in pay for doing the same duties and having the same responsibilities), then list them as separate jobs with the same employer.
In the military, I had like 4 different billets over 4 years. I didn't want to put "Military for 4 years" because it's a little broad, and just one billet wouldn't encompass all the skills I could present to an employer. I think it would be odd if you list the responsibility of "washing dishes" under the position title of waitress. If I had seen it, I would be thinking, "Uh, isn't that what the dish washer does?" Obviously I would conclude that you had, in fact, been in both positions, but only after I would have backtracked to understand it.
It's the same thing generally, IMO. If I were a store clerk for a year, but then was promoted to that store's manager for another year, I wouldn't list that I was a store manager for 2 years and also have the duties or responsibilities of a clerk under that position - they may assume I was performing duties of a manger and a clerk at the same time, which IMO is misleading.
EDIT: Once you start to claim some more work exp through internships or other jobs, then you'll realize that you may not need to include dish washer or even waitress depending on how you're trying to focus your resume to a specific employer or position.
For example, if you're a chem major interviewing for a lab job after graduation (assuming you have a couple internships by the point), you may want to leave off the dish washing/waitressing gig all together and really focus on the chem internships you have over the last several years. If in the interview they ask you something like, "So, you're resume didn't show anything before your Sophomore year of college. Were you only focusing on studies at that time, or trying to find out what you were interested in?" You could simply reply with something like, "Well actually I was waitressing thorugh my Freshman year from a job I had secured the Summer before. I really liked the people I worked with and liked working together with them to make our resturant a great experience for people, but by Sophomore year I began to get involved with things that were more along the lines of my career interests."
Last edited by turtlerock; 08-09-2012 at 12:47 PM.