First of all, I still got a question to Android which is why they don’t directly provide such a good solution to user to directly taking a screenshot such as iPhone.
Ok, now you may refer to this article on how to taking a screenshot from Android phone.
1. Check if you have the Java SE, if not then install it.
2. Install latest Android SDK, download the installer if you want to install it or download the zip file and extract it.
3. Connect your phone to PC.
4. Enable the USB debugging. If the application is not pop up, use the step as below.
Home -> Menu -> Settings -> Applications -> Development -> Checkbox USB debugging.
5. Open your extracted Android folder or installed Android folder.
6. Open tools folder and click on ddms.bat file.
7. Open the ddms manager where you shall see your application list from the left box.
8. If you do not able to see your device listed, install the ADB driver by referring to article here.
9. Select the device and use Ctrl + s to enter the screenshot page.
10. Now, you may save you image from the console.