Check with your manufacturer's web site for battery care. Hewlett Packard (COMPAQ) has a good treatment of this, as well as sowfware you can download to see what's happeing with the battery.

I keep my COMPAQ plugged in all the time when at home. I'll sometimes decrease the brightness of the display to increase the run time when traveling and on battery. There are also different modes you can set for different kinds of battery management for most brands, but I don't worry too much about that.

Expect your battery to show gradual degradation after about 1 1/2 years no matter what you do. Replacement is usually a good idea after 2-3 years since you will likely be down to an hour or less of battery run time. Check the web for third party battery replacements as they can be up to 50% less costly than buying from the manufacturer. Also, some brands will accept a larger battery if you needed extra run time and can stand the added weight.