I applied to the Adult Interdisciplinary program. Other students should talk to the administrators of the school in which they are interested in securing a degree.
USA's policy on admissions seems to be "if you've got the money (or the financial aid coming in) we'll take ya!". Just apply and send them their $25 bucks application fee and they'll likely accept anyone.
To get into my university I applied, sent a highschool transcript, and my ACT scores. I reccomend having an ACT score higher than 20 and if possible 26 or higher as academic scholarships are available at that level. Apply for financial aid early.
Application to the university wasn't that hard (one page front and back). But if you have a good high school resume, try to get into the Honors Program (offers a scholarship) its a real privelege to be accepted and it introduces you to a wonderful group of people. The director of the program is incredible.
If you wish to further your education, consider one of the many options available through online degrees. Browse a wide range of online college and university programs and find the perfect degree for you.