Apple - How to take a screenshot on iPhone X?

Hold the Side button and tap Volume Up.

#iPhoneX screenshot: Side button + Volume up

https://twitter.com/reneritchie/status/907736291726336000

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.