Put the computer to sleep by tapping the power button so the sleep menu comes up, and then click sleep. Alternatively, you can go to the Apple menu and select sleep from there.
Once the sleep light starts blinking and you've confirmed the hard drive is no longer spinning, carefully close the lid so that you don't reactivate the computer.
Then remove the battery. The light will go out. The computer will be dead.
Now, either connect the computer to AC power, or put the battery back in and restart the computer.
You'll see a progress bar and then the computer will return right where you left it. Enjoy amazing your friends.