I teach at the UNT med school. While the overall GPA is important, the grades in prerequisite science courses count more heavily in the overall evaluation process. If these courses are going to be taken outside of the student's major, make sure these are not done at a less rigorous institution (summer school at a community college, etc.) as this will look suspicious.
Also, recognize that most medical schools are extremely concerned with students dedication towards being a physician (med schools cannot afford drop-outs, they can't just replace a 2nd year burnout with a random person off the street). While it is not unusual to have students with "non-typical" majors apply to medical school, these students generally need to explain why they decided to transition from business or engineering to medicine in their application essays since it can look like they've previously waffled on career choices.
Additionally, to demonstrate dedication to becoming a physician, volunteer and shadowing experiences are now essentially required by all medical schools. Ideally, such experiences are accumulated over time and not right before applying to medical school.
I cannot over emphasize the value of an MCAT preparatory course. An MCAT score of less than 500 is pretty much a deal breaker regardless of GPA. A great MCAT can go a long way in compensating for a lower GPA. A 4.0 GPA, even from a highly regarded school like A&M, can't compensate for a bad MCAT score.