Since iOS started the process of taking a screenshot, press the sleep / wrench and home button simultaneously. The screen should flash, leaving a camera will stop sound and the screenshot would be saved in the camera bar.
With the resurgence of iOS devices that lack a home button, starting with iPhone X and now the new iPad Pro, the everyday task of taking a screenshot has changed.
To take a screenshot on the new iPad Pro, press the sleep / wake button ̵1; it's the button on the top of the iPad Pro and the volume button at the same time.
You do not have to hold the buttons for a long time. Just make sure that you press them at the same time, and you will notice a screen flash and camera screen noise.