Will Carington, works for Noodle
The answer varies from school to school. You can generally find out what percentage of students receive financial aid at a given school on their website, usually on the financial aid page or the admissions page. Noodle also provides that information on each college profile. For example, the "Finance" section of the University of Texas at Austin's Noodle profile shows that 54% of students at the university receive some form of financial aid.
If you have questions about financial aid at a particular school, you should contact their admissions office or their office of financial aid. A financial aid officer will be able to provide detailed information about exactly what types of aid are available (federal and state grants, loans, merit scholarships, etc.) and can answer questions about the application process. Useful information and advice can also be found on Noodle's financial aid resource page.