Speak with an admission's officer. Arrange a time to meet with an admission's representative from a college or technical school you want to attend. Learn if it has a special admissions category for students without a high school or GED diploma. For example, some allow a person to register as a guest student or non-degree-seeking student. This gives you time to take a few courses and score a high grade point average that qualifies you for admission as a full-time, degree-seeking student.
Prove you're able to benefit. The U.S. Department of Education has created the ability-to-benefit category, which allows students to take college courses as a full-time, degree-seeking student if they are able to show they can learn and benefit from the courses. Take the three tests--reading, writing and math--that determine whether you are able to benefit. Know what minimum scores you need in advance and make sure you get these to be admitted and start taking courses.
Get permission from high school. If you don't have a high school or GED diploma yet because you're still attending high school, learn what is required for you to take college courses at the same time you're in high school. Find out whether a special permission form is required from your high school counselor or principal, and get it filled out and returned to the college. Understand that your ability to take college courses while still in high school may depend on your high school grade point average as well as the number of courses you want to take.