What should an artist first do in order to render any subject as realistically as possible?

Draw the details of the background.
Draw the details of the main subject.
Roughly draw the main subject to fit inside of a pyramid.
Roughly draw the proportion of the main subject.

The first step an artist should take in order to render any subject as realistically as possible is to roughly sketch the proportion of the main subject. This will help in establishing the correct size and placement of the subject within the composition before focusing on the details.