I know: it’s a rather old trick. But, always worth knowing.
You have basically 3 ways of screenshot. What method you use is up to you.
Standard Android way
Press in home and volume buttons at the very same time, keep pressed until you hear a camera shutter sound. Will give you a notification where you can easily share that screenshot.
HTC way via buttons
Keep power button pressed shortly and tap home button.
HTC way via quick menu
Just swipe down from notification bar with TWO fingers (important) or single swipe and tap quick menu button. Then you just tap the screenshot button, you might have to edit quick menu first (the edit button on top) to have it visible. Just find it and drag it to where you want it. Then just swipe down and tap screenshot. Done. Gives you a notification as well.