Grades and coursework
Making the grades
Choosing a major that you care about will aid in achieving the grades you will need to gain admission. Why? Because the odds are you will care more about your work! This is key - the averages of my incoming IUSM class were somewhere around a 3.73 cumulative GPA and a 3.7 science GPA.
SCIENCE GPA?! What? I thought you just said I didn't have to major in a science!
Yes. Every medical school requires their applicants take science classes - some medical schools even require that you take calculus too. These science classes, cumulatively, will be the "pre-med coursework" you must complete in order to take the MCAT and apply. It will include studies in the general principles of inorganic/general chemistry, organic chemistry, biology, and physics. If you will be taking the MCAT in 2015 or beyond - Psychology, Statistics, and Ethics and Cross Cultural Studies (i.e. Sociology) will be tested on the MCAT, but you should already be taking classes like these...
If you have chosen to major in anything other than a science, the science GPA becomes much more valuable. This is because medical schools will want to see that the student is able to handle scientific course work well. Therefore, that 3.7 average is much less forgiving. However, if you do major in a science, don't think you can slack off, you still must perform well. Once you have signed up for your science classes, try your best to get straight A's in all of them. Not only will this help you keep a high GPA, but it will also better prepare you for the Medical College Admissions Test (MCAT), wherein those classes previously named are tested. Also try not to skip class. Your professors will not like this, and you will fall behind very quickly.
Here is some Pre-med Science Help
So, now that we've talked about your premed courses, what about your other classes? Do well in those too - read your assigned readings, turn in your papers on time, and learn how to time manage well - this is a very important skill that you will need in ANY career.
Next, it is a must to become involved in clubs and volunteerism.