This is super handy if you need to quickly show someone something – I use it all the time! Follow these steps:
1. Locate what you want to capture (eg. a webpage/etc.).
2. Hold down the sleep and clicker buttons simultaneously – the device should make a photo sound.
3. The screenshot will capture and shrink to the bottom left of the screen.
4. From there, you can tap on it to open and edit/crop it or save it to your photo album.
Tip: you can share the item at this point, rather than saving it. Also, on the newest iOS devices, the top volume button replaces the clicker button.