He inquired, "How do you construct a sketch? Do you start with the head or body...do you use some sort of gesture line to capture movement?"
The answer is that it all depends on the action being drawn.
The majority of my sketching focuses on people and animals in movement. Observation plays a key part in any drawing, more so in true quick sketching (my book gives an in depth definition).
The general rule is to get the head over the weight bearing foot or triangle shape for a balanced sketch. You have to work at this for it to become 'second nature' to you.
I usually start with the head and drop a line (visually) straight down to the foot that is bearing the weight.
As an example, the below man is carrying a weighted object (baby in basket). You'll see his head is directly over his weight bearing foot and counter balanced by the arm away from the body.
When sketching sports action the idea of head over weight bearing foot does not apply as most activity is 'in the air' or in an extreme pose. A gesture line or basic shape is what I look for.
For really fast action as in these skateboarders (below), I use whatever it takes to capture the pose. After a period of time spent observing arms, heads, bodies in contorted shapes and all at break neck speed and in constant movement trying to stay balanced upon a small rolling board, I'll begin the sketch.
A gesture line here, foot placement there, deciding what shape this pose represents is about all I can do to put this action on paper in a split second of time.
Below is a Long jump series. Starting with a backward c shape, into a forward c, and landing as a triangle (my interpretation).
By the time I finish these three sketches, the jumper is walking away from the long jump pit.
Animals also have to feel on balance. Weight over feet (paws, hoofs, claws).
In quick sketching try to choose a subject(s) that is engaged in some activity, that makes your sketches interesting and fun to look at.
But remember to spend some time observing your subject in action BEFORE you put pen to paper.
For more information and helpful hints on Quick Sketching, check out my book on Amazon.
Until next time...Happy Thanksgiving!