High GPA and High Test scores are very important. Also, for most BS/MD programs, you have to write a personal statement, get recommendations, and do an interview. Additionally, you’ll be evaluated on your extracurricular activities. These programs want to see that you’ve demonstrated leadership and achievement; furthermore, they like to see involvement in extracurriculars related to health and medicine.
Basically, getting into a BS/MD program is on par with getting admitted to the most selective colleges in the country.