They really only do take pretty bright and qualified applicants. If you make it through a fairly easy first round interview, they make you take a 3 hour skills test. this includes everything from typing speed to basic accounting. They hire you based on those results. I didn't get the job my freshman year when I applied because my typing was horrible and I didn't have any specialized skills. I did get it the second time around (2 years later).

If you do poorly or are unprofessional at the place you temp at, they probably won't call you again. I was working at the San Ysidro ranch fairly regularly, but one of the temp agents didn't tell me I was working a certain shift, so I missed it. I didn't get called back for that job, even though it wasn't my fault. Just make damn sure you are on time and don't mess up.