Despite what some students consider a nail biting experience, office hours for pre-meds are particularly important because they provide a means for professors to get to know students so that those faculty members can write strong letters of recommendation. I have a doctor friend who told me that he went beyond traditional office hours: During his undergraduate years, he got acquainted with a few professors by inviting them to lunch at his dorm. He had to call several times before one professor got back to him, but once they did have lunch, my friend's opportunities really expanded. That professor realized my friend's intellectual potential and good nature and offered him a position on an honor committee and a strong medical school recommendation.
As they say in the NPR broadcast, "... when you go to office hours, you're actually letting the professors do their job."