I wish I had known which material was going to be the really high yield material later on (obviously that's not always possible). I had a couple of math courses (e.g. linear algebra) that I absolutely hated and put very little effort into, learning very little, only to find out that the concepts from those courses would be the cornerstones of much of my later coursework.
If I were back in college, I would try to find out from older students, grad students, and professors what they considered to be the most important concepts to learn for my major/field, and make sure I had those down pat, not just for the test.
If someone had said, for example, "you need to understand eigenvalues, they're really important, you will use them all of the time", I probably would have paid a lot more attention and tried to get something out of it that first time around, even though they were completely abstract and without context.
If I were back in college, I would try to find out from older students, grad students, and professors what they considered to be the most important concepts to learn for my major/field, and make sure I had those down pat, not just for the test.
If someone had said, for example, "you need to understand eigenvalues, they're really important, you will use them all of the time", I probably would have paid a lot more attention and tried to get something out of it that first time around, even though they were completely abstract and without context.