My dad always used to cite the chinesse proverb "the palest ink is better than the sharpest memory.” And heeding his advice has been very good for me, for sometimes with so many things going on at school, at work and at life I can´t keep track of were I left my mind, much less of what I have to do. So the solution is simple: I use agendas.
I've never tried anything fancy like GPA´s, because, as I mention, I haven´t lost my head just because it´s attached to my neck; and loosing something expensive like a GPA is not something I want to do. But I like to write, kinda old-school, in a weekly planner. Schools usually give free agendas to their students (or so has been my experience), and I seem to like those, although you can go to any departamental store and find one that suits your interests. I like them easy to carry, not too small-not too big (i know, difficult to pin-point) but the less bulky possible.
So, when professors give their syllabus, I write down all deadlines in the semester there. And whenever a meeting pop-up, I also write it down on the specific day. I sometimes have to number things around to see what I must do first on a day when I have a lot written down there. I also keep track of other things, sometimes, like "that day of the month," birthdays, and days were I had a lot of fun, I write down why. I have agendas from my junior-high school, and every now and then I open them and find myself remembering that extra-big-evil-project that had me throw an all-nighter and that is marked as such in the day it was due. It is kinda like a diary, but of activities.
(Which makes me think: perhaps blogger needs some sort of an organic friendly application for doing journal-log-agenda's posts.)
Anyways. That is my suggestion: keep an agenda.