Probably a novice question, but how do I correctly diagnose from a photo for what reason that camera wasn't able to focus properly?

It can be any 1 of the following

 - Unsteady hand
 - Lens issue
 - Metering
 - Re-Calibration required in camera
 - or ...

Is there a set of unsaid protocols that needs to be followed by a photographer?

Goal is to get a sharp and crisp image prior to editing.

[PS: I own a Nikon D5200.]