You have to understand the following 3 types of classes:
1. Doesn't matter how many office hours you attend, everything depends on your intelligence
2. Going to office hours actually really helps
3. Doesn't matter if you go to office hours or not, you are probably though going to be helped in office hours because you get the LOR
Premed is absolutely doable if you are smart and you know your capacity. If a kid who has done terrible in HS comes with the 4.0 mindset, it is wise that the student make the semester courseload easier at the beginning and catch up by taking summer classes (but of course some summer courses are not suited to be condensed so choose wisely the classes you take and with who you take them with), as opposed to rushing since they may not have AP credits to get ahead.
If you are smart, don't be overconfident with your potential. Look at professor rating and don't put yourself with a professor that is terrible just because you do great regardless...even if the class average is a 45 and there is a curve, there is no gaurantee you will get an A even if you think you are an above average student. Pick the professor that is straightforward. Some professors that are straightforward may still have averages around 45 so that can be deceiving.
Be proactive about seeking opportunities. Seek out fellowships that you can obtain early so that you can plan ahead and finish most of everything by end of junior year for app season to see.
Spend as much time in the library as you can but realize that once you find the key to succeeding in your classes, it is okay if you decide to reserve some tickets to an athletic game and see university life. This experience comes once in a lifetime but do not sacrifice your education for it, it should only be used to deflate from the stressors around you.
Do not waste time being neurotic. Ask people what they are doing, how they are doing it, but do not be that kid that constantly compares. Pick a major that is useful...not by and large theoretical and not applicable...should you fall in the gap year schemata.
When mapping out summer activities, if you take classes in the summer, try fitting in hospital volunteering and shadowing as small time commitments so that you won't stress about them later.
If you happen to find REU and other things enticing, prepare applications for it during winter break and ask your professors ahead of time so that you can apply to as many programs as possible.
Your career services also hosts a lot of summer programs/internships with possible employers. Just because you are a traditional applicant, don't pass those up. Go to them, meet with people, understand their interviewing process, and get the position if you like. It'll teach you about something unique.
Take the MCAT the august that is 1 year prior to your app cycle!