Pencil Sketch.

 Tips 

*When painting with water, move from lighter areas to darker areas. The brush will carry the darker colors into the light areas if you do not do this.
*Your pencil marks and brush strokes should go with the contours of your subject.
*If you plan to add a background, you should do that first.
*If you notice an area is too dark before adding water, use a kneaded eraser to lighten it. Squeeze the eraser and press it flat against the area to be lightened. Peel it off, stretch and roll it, repeat till it's lightened. This is gentle enough that it won't damage the paper surface the way rubbing with other types of erasers will.
*Don't add pencil to wet areas; it creates a darker colour that won't change.
*You may be able to remove small errors by adding more water and blotting it with the paper towel. This is particularly good for lightening small areas if you've lost a highlight. Once it's dried, it may still work depending on the brand of watercolor pencil. Derwent Inktense and Faber-Castell Albrecht Durer watercolor pencils do not re-wet and can't be lightened once dry, but Prismacolor Watercolor Pencils, Derwent Graphitint, any graphite Sketch and Wash, Derwent Watercolour and many other brands do "reactivate" if you dampen them again. Paint the highlight with clean water and gently blot to lift color. Repeat as needed unless it starts to damage the paper surface.
*Test unexpected color combinations on a side sheet of watercolor paper or a multi media sketchbook. Try mixing complementary colors like orange and blue or yellow and violet. See whether mixing two dark colors like Indigo and Dark Brown may make a richer black than the black pencil. Sometimes layering the very bright colors in the right order and the right combination can give richer browns and grays than using the brown and gray pencils.
*Try a waterbrush - a nylon watercolor brush with a plastic handle that has a water receptacle in it providing a steady flow of water to the tip. These are available from Niji, Derwent, Sakura and several other manufacturers. Immensely convenient for watercolor pencils, you clean them just by swiping them on a cloth till it runs clear again before changing to a different color area.
*Shade lightly and evenly, deep marks may remain or groove the paper in places where you don't want them.
*Sometimes it can even be useful, if you are going to blend many large patches of colour for a background, to paint the whole sheet lightly with water. Before it dries, add the pencil layers on top and then yet another watery layer for a wishy- washy effect.