Installing the Jupiter power management application
This is an optional install, but I recommend it for laptops, as when you switch from mains power to battery power, the Jupiter panel applet will switch your CPU into power saving mode, which will make your battery last longer.
Open a terminal and run
sudo add-apt-repository ppa:webupd8team/jupiter
sudo apt-get install jupiter
Now REBOOT (to load the application) .. you'll then see a new icon by the clock that looks like a lightening bolt .. when you unplug the mains power, this icon should change to reflect it has set the CPU to "Power Saving" mode, when you plug it back in, it should switch to "Maximum Performance" mode.
You can also switch modes manually by clicking the lightning bolt icon, and selecting the "Performance" mode.
Be aware .. with certain laptops, the switching to "Power Saving" isn't 100% accurate .. so when you unplug your laptop from the mains to run on battery for an extended period, visually check the icon has changed to "Power Saving" mode, if it hasn't, do it manually .. and if necessary switch it back to "Performance" when the laptop is plugged in.