If you hope to attend a public or private university after finishing up your general education at the community college, you must provide the following to be accepted: your SAT/ACT scores, placement tests scores (you can take the placement test at the junior college), your transcripts from your high school (which must be an accredited school), a filled-out application for the college and the application fee.
Many community colleges have an "open to all' enrollment policy. If you are wishing to take general classes just for fun, you must: be over the age of 18, pay the admission fee and submit a filled-out application for the college.
It is not uncommon for high school students to attend junior colleges in addition to their high school courses. This allows them to get started on their college career before they even graduate from high school. A high school student looking to enroll in a community college must have: completed the vital high school graduation requirement classes, a 3.0 or higher GPA and a letter of recommendation from the school's counselor.
International students can attend community colleges, however, they must make sure that their visa permits them to do so. The best thing to do would be to check with the U.S. Citizenship and Immigration Services to make sure it is alright to enroll into community college whether you wish to pursue a degree or just take courses for your own enrichment.