In public places, like the library, work, or even on a laptop in a cafe – make sure to lock your desktop when you walk away from your computer. If you don’t, you could leave yourself open to pranksters updating your Facebook or Twitter status. Even worse, depending on how much time they have, they could potentially steal some personal information.
On a PC, you can lock the desktop by hitting the Windows logo key and “L.” On a Mac I think it’s Spacebar (or Command-Y).

{ 2 comments… read them below or add one }
This is a valuable tip. Many people just don’t realize the dangers of not protecting their data, and the nefarious individuals out there trying to cause… nefariousity.
No, no no… terrible advice. What the hell am I going to do for fun all day if people like you lock their computers?