1. Simultaneously press and hold the power and volume-down buttons.
2. Swipe the edge of your palm across the screen from right to left (this will need to be enabled in Settings > Advanced Features > Palm swipe to capture).
3. Use Smart Select to capture a specific area of the screen. This is available from the Edge Panel, where you'll find both rectangular and oval options.
4. Ask Bixby. Press and hold the Bixby button and say 'Take a screenshot'.
After the screenshot
Once you have taken your screenshot you have some additional options pop up at the bottom of the screen for cropping, editing and sharing that image. You'll also find Scroll Capture, which enables you to take a longer screenshot - handy if you want a screengrab of a message or web page that would otherwise require you to scroll down and capture and then stitch together multiple screenshots. It's not infallible, but most of the time it works great. Give it a try.