1. Sleep Is Good
Use the operating system's power-management features (in Windows XP, under Power Options in the Control Panel; or in Vista, under Mobile PC in the Control Panel) to set aggressive targets for when the display will go dark (say, after five minutes of inactivity) and when the machine will slip into sleep mode (no longer than ten minutes of inactivity). And if you can spare the extra time it takes for the machine to resume, set the PC to hibernate, not just sleep, when you close the lid.