Assuming your school works on a quota, then getting a high grade depends a lot in the competitiveness of your classmates. If your school has a rule that stipulates that no more than a %age of students are allowed to get a A- or better, and your class is full of ambitious pre-meds, then it would be cut-throat. Working hard and having good studying skills is THE LEAST you should have if everyone else has works just has hard or has the same efficient studying skills as you. In such situation, you have to be SMARTER (i.g. memorize, assimulate material more quickly) than the others to pull ahead and make sure you're one of the few who get that coveted A-/A/A+.
I recall my second year biochem class: everyone had a 3.4+ GPA from first year, to due to the biochem department's regulations on class enrollment. You won't believe how many 3.8 GPA pre-meds got discouraged after getting a B- (GPA of 2.7, also the final class average) in the course. Not everyone gets to go to med/dent school.
