The best internships are often unpaid or offer a small stipend. The prinicple reason for interning is to supplement your education, to strengthen your resume, and to establish professional contacts. Remember, many interns work part-time jobs to supplement their internships. Identifying internship opportunities is the first part of a large task. You should begin your internship experience 6-9 months in advance of the time you would like to start work.
Many companies have deadlines for applying to internships.
Regardless of the deadline, however, beginning early illustrates to employers that you are on the ball and immediately distinguishes you from the majority of students, who wait to the last minute to apply. With few other discriminators among the applicants, this will give you an edge. The second advantage to beginning early, is that it will help you to better screen the opportunities available to you and allow you to make a more informed decision. Focus your search on those positions and companies in which you are most interested and then sell yourself to those positions. When you have identified the opportunities you are interested in follow through.