Going to school where college is cheap and/or cost of living is low.
Testing out of classes.
Taking a job where your employer will pay for your education.
Living with relatives while attending school on a pay-as-you-go basis.
Different people work this out different ways. The exact details will vary tremendously.
I have done all of the above at various times. I have nearly six years of college and only ever took out one student loan for a boot camp style summer program where I completed a year-long certificate program in eight weeks.
How do?