One of the worst things that can happen while working on a laptop is to have your battery die while you are in the middle of an important project. To avoid this, it's good to know how much life your battery has left in it. Most laptop computers offer a couple of ways to do this, and there are several free downloads that will put a large battery-life monitor on your screen, meaning you'll never be caught with a dead battery unexpectedly again.
Look in your computer's system tray, which is at the right side of your taskbar near the clock. You should see a battery icon. If it doesn't show up automatically, click the arrow on the left side of the system tray, which will expand the tray and show all icons.
Place your mouse over the battery icon, but don't click on it. The icon will show roughly how much life is in the battery.
Hovering your mouse over it will pop up a label showing exactly how much time remains before you run out of power and what percentage of the battery remains charged.
Plug in your AC adapter if the battery needs to be charged. The status in the system tray will show that the computer is now running on AC power, and the battery is charging.
Many sources recommend letting a battery fully drain, so as not to shorten its "memory." However with Lithium-ion batteries, the most common type of battery in modern laptops, this is not the case.