Here's how you can take a screenshot on Samsung Android devices. This tip may or may not work on other Android devices, but you can give it a shot and see if it works.
1. If you are using Android 2.2, hold the back button and push the Home key.
2. If you are using Android 2.3, hold the Home button and press the Power key.
Your screenshots will be saved in a folder called ScreenCapture in the root directory of your SD card.
For more, see the original article at the link below.
How to Take a Screenshot from Android Device | Androtweak