Internships and co-ops prepare students by giving them real-world experience in a career field that's of interest to them. There are many types of internships and co-ops available; but today I am focusing on opportunities that are specifically targeted toward students of color and under-represented groups.
Organizations like SEO, INROADS, Management Leadership for Tomorrow, Co-op / internships and summer research opportunities for minority students, National Association of Black Journalists, and The Yale School of Management Pre-MBA Leadership Program all offer a chance for students from minority or under-represented groups to get a chance to gain real-world experience in the workforce.
You can use these resources to get started and then do some research to find other opportunities in specific career fields that might be right for you.