How to take screenshots in my Android phone

How do I take a screenshot on my Android device (e.g. smartphone or tablet)?
hold down at once Volume Down and Power for 1–2 seconds = The screen flashes white. Your device captures the entire screen and saves it as a photo.

Where do I find my screenshots?
Look for a Screenshots folder in your Gallery or Photos app.

I see no flash and no screenshots. Is there something else I could try?
hold down at once Home and Power for 1–2 seconds = The screen flashes white. Your device captures the entire screen and saves it as a photo.

It still does not work. Why?
On most devices you need Android 4.0 or later. However, you could try using an app instead.