This is an HB pencil sketch I made a couple of years ago during a workshop at The London Atelier of Representational Art. They teach the sight-size method which is a technical way of drawing that involves careful observation and making sure that you draw exactly what you see on a one to one scale.
To do this you have to stand in exactly the same position and by building up a drawing starting from broad shapes you can then slowly build up detail.
Attention to detail is the key and there are a number of methods that are taught to make sure that your drawing is accurate. The aim is to get to the point where using plumb lines and other measuring tools aren’t necessary as you are so used to accurately measuring that you don’t need to do it consciously.
I don’t believe that accurate representation is the only thing that’s important for an artist but I do believe that to understand art it helps to gain as much experience as possible using a variety of techniques.