Method 1
Here's how to do it:
- Get the screen that you want to capture ready to go.
- Simultaneously press the power button and the home button. It can be a bit of a stretch on these larger phones, but it works. You'll hear the camera shutter sound fire off, and that's how you know you're good to go.
- You'll now be able to see the screenshot in the Gallery app, or in Samsung's built-in "My Files" file browser.
- If you need to find the screenshots from a command line or through the Android File Transfer tool, they'll be in /pictures/screenshots.
Method 2
I bet you didn't know this. It's not new to Samsung, but it's still pretty neat, and it's enabled by default. Tilt your hand up onto its side, with your pinky facing down. Now swipe it across the screen, and make sure you actually touch the screen.