Yesterday I talked about using wired networks instead of wireless. If your computer has a wireless card and you are not using it, turn it off. A wireless card will use up your battery even if you are not connected to a wireless network.
My laptop has a switch that turns off the power to my built-in wireless card. One of my kids has a laptop with a function key that does the same. If you have an “add-on” PCMCIA wireless card, take it out of your machine when not in use.
Leaving your wireless card on can also cause some security problems. Someone that “sees” your computer via a wireless adapter can mess with your machine. There is already a “Free Public Wi-Fi” sort of virus going around.
There is a hard and fast rule you should follow regarding all computer software. If you are not using it, turn it off. Wireless should be treated the same way.