How to take a screenshot on iPhone X?
Solution 1:
Hold the Side button and tap Volume Up.
#iPhoneX screenshot: Side button + Volume up
https://twitter.com/reneritchie/status/907736291726336000
Solution 2:
Two Methods i found on Google,
Method 1:
Using Press, Side Button + Volume Up button at once.
Source: Take a Screenshot on iPhone X: Alternate Ways
Method 2:
Using Assistive touch, Really great for use on lock screen, Home screen or App Screen.
Solution 3:
One alternative way could be to use the new screen recording feature in iOS 11, and then from the video choose the image of choice.
Solution 4:
You apparently can do it by pressing the sleep/wake and the volume up button at the same time. Nevertheless, you can still take a screenshot with Assistive Touch in settings.