Draw pine trees with a pencil in your sketchbook. Erase whatever you don't like. Or you can always turn to a new page and start another sketch.
Draw the main trunk as a round cylinder and the bunches of needles as one three-dimensional mass.
Draw a few close-up sketches of the branches or pine cones.
Make several detailed sketches until drawing the tree seems natural.
Make the preliminary sketch on watercolor paper or Bristol board with the pencil. Use the eraser as needed. Let the tree take up most of the space on the paper without worrying about detail.
Wet the tree areas with clear water and then fill in the trunk and branches with a mixture of burnt umber and burnt sierra. Mix the paint with ample amounts of water.
Wet the foliage area and fill these areas with sap green. You can mix the sap green with a little yellow ocher if you like.
Do a quick coverage of the foreground with a wet wash. Try and match the color of the foreground with whatever paint you have.
Repeat for the background forest area.
Wet the sky area with a wide brush. If the weather is cloudy or hazy you can use dirty water to prep the area. Add a wet wash of cerulean blue. Use clear blue cerulean, if the skies are cloudless, or a blue mixture if skies are hazy.
Add details to all areas of the painting except the sky.