Sketching is a good way to build your composition with simple shapes, lines, and tone. Nobody has to see your sketches, and they don't need to be refined; just start sketching. Start with simple shapes, and build upon that. Your sketches can fall into three groups.
A Croquis is a thumbnail sketches that establish the image's main concept and sets the composition by indicating the most important shapes and values.
An Esquisse is a refined version of the Croquis: a more resolved thumbnail with a refined value structure and something closer to the final composition.
Is a drawing of an individual natural element, such as a tree, a patch of undergrowth, or a rock outcropping.