Only 25% of jobs make it into the newspapers or onto job posting boards. Ads cost money–it makes sense to spend 75% of your time applying directly to employers, and only 25% of your time answering ads.
Spend the time. While you are in school, make two calls a day. If you do it right, a job search is an almost full-time job. You should spend four or five hours a day on it. Play and pray the rest of the time.