Put your computer to sleep when not in use) - If you're taking a break, let your computer take one as well.
Remove the Dell Alienware M11x laptop battery if the notebook will be stored (turned off and not plugged into AC power) for more than 2 weeks.
Try to avoid using a PC Card adapter, as they can drain your battery quickly, and make sure that your USB devices are set to allow Windows to shut them off to save power—you can find the settings in device manager's Power Management property pane for the device.
Make sure to discharge the Dell Alienware M11x battery sometimes, and if you spend most of your time plugged in at a desk, you would be better off running the battery down to half, and then simply removing the battery and storing it in a cool place.
Use the right adapter - Ensure that the adapter you use to charge the laptop battery is an original one or one with the correct specifications. A mismatch in the wattage could cause an overload thus damaging the laptop and the battery.