 
Pre-medicine is NOT a major and there is no "correct" major for pre-medicine. While most students major in a science area like biology, chemistry, or math, a major in science is not required. Because medical schools seek candidates with diverse interests who are capable of handling rigorous science courses, students with backgrounds in liberal arts and business are also successful. So the best advice is to select a major in an area in which you are interested and in which you can do well.
USI is proud to offer the 1st Pre-Medical Sciences Certificate in Indiana which helps provide curriculum, advising, and support for pre-medical students of any major at USI. Our goal is to help you have the undergraduate experience you want and to reach medical school successfully.
All medical schools in the U.S. and off-shore have similar requirements for acceptance into their programs. The minimum set of required courses typically includes:
In addition to the required courses above, there are several courses to consider which will prepare you for the coursework you will encounter in medical school. Courses to consider include animal physiology, genetics, anatomy, physiology, microbiology, immunology, and histology. None of these are required for admission to medical school.  
For specific requirements for medical schools, review the AAMC Required Premedical Coursework and Competencies.
The grade point average (GPA) is an important component of the requirements for admission to medical school. It is not necessary to have a 4.0. Instead, it is probably better to have a solid GPA in the 3.80-4.00 range (on a 4 point scale) and participation in extracurricular activities to demonstrate interests beyond academics. If you have a poor first year but steadily improve in the following semesters, you still have a good chance of admission to medical school. However, if you start strong and then fade, your chances for admission could be diminished.
You should begin the formal application to medical school during the summer before you graduate because it takes about a year to complete the entire process.
Almost all allopathic medical schools (MD programs) in the U.S. participate in the centralized application service, American Medical College Application Service, (AMCAS). This is a computerized application process requiring students to designate the school(s) to which they are applying. Students will complete the application forms online. AMCAS verifies all the information and forwards the completed applications to the designated school(s). The school(s) review the application and determine if the student is qualified to receive a secondary application. The secondary application may be as simple as a request for letters of evaluation or as complex as another application. Once the secondary application is complete, the student will be invited for an interview.    
Students interested in applying to osteopathic medical schools (DO programs) can use a similar system through the American Association of Colleges of Osteopathic Medicine Application Service (AACOMAS).
Students who need financial assistance to complete the necessary standardized exams and applications should apply to the AAMC Fee Assistance Program or the AACOMAS Application Fee Wavier. For more information on the cost of medical school applications, see this outline provided by the AAMC.
Timeline
MCAT Preparation Resources
Shadowing experiences are an important part of your pre-medical training. Not all medical schools require shadowing, but all highly suggest it. We suggest a minimum of 3 significant shadowing experiences. You should choose experiences in a variety of specialties that last a least 1-2 full days each. Spend time researching all you can find about the medical profession and consider how the demands of the career fit with your lifestyle. Occasional volunteer activities or summer work is another meaningful way to learn about the profession. While the importance of these types of activities varies with different medical schools, the experience you gain cannot be measured.