How can I stay organized in school?

I am a major procrastinator and very disorganized. I did okay my freshman year in high school, but next year, I want to do great, because I know I am very bright and could probably have a 4.0 if I set my mind to it. What is the easiest way to stay organized and on top of all assignments, as well as beating procrastination? [The most specific answer will get best answer.]