To my fellow sketchers, here is a brilliant blog-post on getting ready to sketch (or draw, if that is what you prefer to call your actions), written by Roz Stendahl at Roz Wound Up

Why Warm Up When Drawing?

a short excerpt:

I do warm up sketches in my journals because

1. I want to connect my hand, eye, and brain immediately. I want to announce to myself that I’m getting ready to work. Pay attention self! Take a deep breath. Here we go.
2. It’s fun to move the pen (pencil, brush) quickly across the page and get a feel for the paper—I’m all about the fun factor of drawing.
3. It’s necessary to start moving your hand and arm about to get a sense of your own physicality on that day and how you are able to move and work in the circumstances—whether you are cramped for working space, or your muscles are cramped from other activities.
4. It’s important to see how your materials and paper are working on any given day in conditions where temperature and humidity effect their interplay. Better to realize in 30 seconds of a gesture sketch (for which you had few expectations) that it’s too humid today to use that sharp-tipped rollerball on the soft printmaking paper, than to dive in and struggle through a whole labored sketch.
5. When you make a quick (30 seconds or less) gesture drawing of a live animal (or person) moving, your mind and eye have to take in the whole gestalt of the subject. In doing that you often hit upon the very essence of what you are looking to capture in that subject. Instead of spending an hour feeling your way to that in a stiff drawing you can realize it immediately and plan your next approach to capitalize on any epiphanies experienced during the warm up.
6. Additionally, quick gesture and contour drawings help your brain identify essential points to gather MORE information on. For instance, a quick contour drawing delineating internal value shapes in crude form alerts you to the need to pay specific heed to those forms and discover in your final drawing that wonderful play of light which first drew your attention to the subject.
7. Perhaps most important for me, warm up drawings actually SLOW ME DOWN. I tend to always be a speed sketcher and when I do warm ups I find that a lot of the excess adrenaline and energy I’m experiencing when I first catch hold of a subject I want to sketch, is usefully drawn off when I do a warm up. When I turn to do a more detailed or studied sketch I find that my attention is focused and a “more accurate” (though I will not say “perfect”) approach is then possible.
8. And an ancillary to item 7—I am able to sync my breath and energy with my subject. This is particularly important when drawing subjects like birds who pick up on my carnivore lifestyle and need to be put at ease. Warm ups allow me to reassure them. By putting them at their ease, they are in turn better models, who work with me rather than against me.

I could continue this list for quite some time, but those are the main reasons I do warm up sketches.

You can read the whole of Roz’s discussion & lots more at her wonderful blog Roz Wound Up