There are certain courses you need to take for medical school preparation, they are known as pre-requiste courses, they prepare you for medical school by introducing you to the foundation of medicine. In addition these courses also help you in preparing for the MCAT. You can find out which courses you need to take by speaking with a pre-med adviser at your school. Usually there is a nice sheet that guides you on which courses to take.
The ones that are required are:
Gen chem 1 and 2
Orgo chem 1 and 2
Biology 1 and 2
Physics 1 and 2
English Composition 1 and 2
Biochem 1 is recommended but I highly advise taking a semester because learning on your own can be confusing for the MCAT and it also helps in preparing for medical school.
Psych/Socio are also recommended
You can also take Genetics, Anatomy and Physiology and Cell/molecular biology as well. They also help when navigating some of the anatomical questions on the MCAT.
If you don't take an intro to Psych or Socio class that's okay, Kaplan and Khan academy help greatly in preparing for these subjects for the MCAT. Definitions, theories and concepts are key in doing well in these sections for the exam.
Hope this helps, best of luck!!