If you want to get a job working at a leading investment bank, your surest route is through an internship program. Most investment banks have summer-long internships tailored to the schedules of students enrolled in four year colleges. While having a summer internship isn't an absolute necessity for landing an investment banking job, such an opportunity lets you demonstrate that you have the capacity for the gig.
Students who have their hearts set on working in investment banking begin early, starting with the college application process. You want to choose a school that has a good finance or economics department, where you can gain some of the basic terminology required for banking. If your school doesn't have either of these majors, you'll be just as well off majoring in mathematics. Build strong relationships with your professors, who may have connections to banking jobs.
Starting in the late fall of your freshman year, begin to apply to internships in the field; if you're at a top-tier college or university, there's a good chance that banks will come to your campus to recruit. Most banking internships are extremely competitive, so try to land as many interviews as you can.
In terms of academic credentials, interviewers will mostly care about your class grades. Your real goal in interviews to show yourself off as a person that would be pleasant to work with, and as someone who has real motivation to start a career in the field. If you have top grades in related classes and can charm your interviewer, you have an awesome shot at landing your perfect investment banking internship!