To make value studies and color sketches? 
As I teach about the art process to young people, I must constantly explain about the need to plan, to sketch and make studies ahead of the finish.
And also that they must slow down,
take their time and not rush to get the final project done.
I have often watched a student prepare a fairly nice watercolor wash and then ruin it with a hasty blobby brushstroke, just because they wanted to finish fast.
Here are my color studies of the sunflower series that I am working on now.
