You can observe a lot just by watching.
Working loose and open can tell a bigger story than a thousand details. Urban sketching is a great practice because the tendency to get nit picky is constantly stifled by life and movement. Sitting for a few moments and sizing up the scene is absolutely essential.
• identify the biggest moments: of light, color, or gesture
• note the parts which are constant and which will move quickly
• capture moving parts in about 3 lines, stating gesture
• make some small marks to indicate how the environment meets this moving part, so when the person/vehicle/animal leaves….you can fill in this info at that time. MAP THE SCENE.
• remember that value has the ability to sum up a situation with brevity and impact