include a high-quality, error-free resume. The thinking goes: if you are not taking care with your resume, then what's to say you will take care with your work?
include a carefully-prepared cover letter that addresses the requirements of the internship and your unique qualifications for it, including your long-term goals, and personal interests.
are appropriate to your background. Apply during early college career for less selective (often unpaid) internships to build the expertise necessary to qualify for more advanced (well-paid) internships later on. Do not spend time applying for internships you are clearly not ready for -- but do keep the information on file for next year's round of applications!
University programs, activities, and facilities are available to all without regard to race, color, sex, gender identity or expression, sexual orientation, marital status, age, national origin, political affiliation, physical or mental disability, religion, protected veteran status, genetic information, personal appearance, or any other legally protected class.