If you have a wireless PC card, you can simply remove it, of course. If you have a wireless adapter built in to your PC, you can disable it. In XP, right-click the wireless icon, and choose Disable. If you're using the adapter's software to manage your connection, check the documentation to find out how to disable it.

If you're using Windows Vista, choose ControlPanel-->Network and Sharing Center. Then in the Connection area, click "View status," and from the screen that appears, click Disable.

Watch out for shoulder surfers

Think all hacking is high-tech programming? Think again. "Shoulder surfers" don't need to know how to write a line of code to steal your password -- all they need to do is peer over your shoulder as you type. So make sure no one seems to be paying too close attention when they're directly behind you.

In addition, if nature calls because you've had too many double lattes, don't leave your laptop unattended when you go to the restroom. Laptop theft has become common in some places, most notably San Francisco, which was subject to a laptop crime wave. Consider bringing along a laptop lock and locking your laptop to a table. Some cafes even include ports to which you can lock your laptop.