When I sketch, I pretty much paint as I see it. Maybe leave out something in outdoor views or paint just the still life items without a background when indoors.
My sketch had no design (fault of the actual scene and my lack of direction in what I do) and to improve it without starting over I decided to add a bigger tree (size) and some birds to give it some depth. It was foggy so there was no big value change in lighting, but I did make the forward tree darker, larger and overlap which in landscapes brings items closer and also to intensify the colors.
It is still not too exciting. To me watercolor is very flat. I'm learning. You need a very light touch to have the paint work so you don't leave strokes in the washes, like the sky. I'm pretty sure watercolor will never be my favorite medium. I am just too impatient to let and watch the paint dry. But I hope to be able to use it better for plein air when traveling so I don't have to take huge amounts of equipment.
In art class we talked about how Elements of Design are important in a painting and to think about before you even start. One element should dominate to give the painting a good start. Elements are Line, Value, Color, Texture, Shape, Size and Direction.
What do you think is the main design component in these three famous abstracts? Think about it before you read on.