I've tried keeping my schedule in electronic format only. For several years I had PDA that I carried. It was glitchy. Even though it could be backed up, it was far too easy for the data to become corrupted. By keeping a hard copy of dates, notes and contact information, I have spared myself a lot of stress and misery.
So, tell me...what do YOU use to keep track of your schedule and important bits of information? I hope it isn't Post-it Notes. I know someone who does that, and the results are, well--sticky.