This video talks about strategies used in the beginning phase of a Boston School type drawing or painting. Also talks more about measuring.

In Response to
Sketchartist

QUESTION: (Re #160 line related concepts) A question about floating lines; is there any kind of measuring going on when drawing these lines? Or are they just "felt" and placed by judging with the eyes alone? I understand perfectly what you're saying about floating lines but I find it difficult to get correct proportions if I don't take measurements.
Sketchartist