Technology isn't going to solve your problem. A PDA or similar item is useful to remind you when something is to be done, but that isn't going to make you do it. If you overschedule yourself, you'll never be able to do everything and you'll quickly ignore the constant reminders because they'll only remind you that you are falling behind.
I work with many people who have PDAs, cell phones and reminders in Outlook and they flounder with time management because they haven't realized that the reminders don't get the work done. They still have to do the work. They aren't disciplined enough to stick to their schedule. Most of them should have a hotkey that activates the Outlook "Remind me in 10 minutes" button because they sit there and click it all day long.
First, establish a schedule that you can accomplish. And look ahead - what's the point of being reminded that an assignment is due today, when you need three days to complete it?
If you find that you can't work on something for hours on end, then break up your schedule into smaller time chunks.
Now, if your question about "time management" was really about "best way to track reminders", then by all means use technology because that will work great.