Preclinical: Honors/Pass/Fail for most classes, though some are strictly P/F. 90%+ is honors, 70%+ is pass. There is also a 70% attendance requirement to honor some courses (I posted about this a few weeks ago, check my post history for details). There's no curve or anything, so theoretically the entire class could honor if we all got 90 or above.
Clinical: Honors/High pass/Pass/Fail. To honor, you need to get an honors designation for your performance on the rotation and score 90%+ on the shelf. If you get one or the other, you high pass. 70%+ on the shelf and pass designation for the rotation is a pass. Again, no curve.
Ranking: There is no ranking until they write our dean's letter for residency application (or maybe for AOA? I haven't looked into it). At that point, we are ranked into whether we are in the top quartile, second, third, or bottom. This ranking is based on some algorithm they use that has to do with the raw number of honors, high pass, and passes we have, and they take into account the number of credits each course was (for instance, our 6 week GI course is weighted heavier than our 2 week behavioral science course). I am an M2 and I don't know what my ranking is right now, but I have a general idea of where I fall in the class based on exam averages and that kind of thing.
Hope this helps!