I have all my classes blocked together so that i feel bad skipping out on any...but other then that i use the Post-It Note system. Whenever i have a big paper due or meetings or exams, i put a Post-It Note on the side of my computer case on my desk. The end of last semester (with finals, exams and end of term papers/lab reports all due together) my case was wallpapered with notes. It helps me so as to not forget anything like that. As for weekly assignments like normal class homework, i just get used to doing it and always due it...