I highly recommend painting on a gray, rather than a white, canvas. White tends to wash out colors whereas gray is much more color-compatible. The canvas can be made gray by using acrylic gesso that has been grayed with either a little black acrylic house paint or with a gray that has been mixed using complementary color acrylic artist's paints such as red and green or orange and blue.
In preparing an un-primed canvas, I typically use two coats of gesso. If the canvas has been primed then I only add one coat. In each case, I sand after each coat using about a medium (about 100 grit) sandpaper.
Sketching the Scene
When I am ready to paint, I sketch the scene on the canvas with pencil and make sure that I like the overall composition before proceeding. Once I have the composition I want, I go over the sketch using a blue paint thinned with paint thinner. This dries rapidly, usually within minutes, and the blue helps preserve the sketch during the initial stages of painting.
The Critical Process Principle
A painting should be developed as a Whole. This is in contrast to, for example, painting the background, then the middle ground and finishing with the foreground. Painting all portions of the work together helps ensure a pleasing composition, balance, and continuity throughout the work.
I, typically, use a two-step or three-step process, depending upon the amount of detail in the painting and the finishing techniques that I expect to use. In most cases, only two steps are required. In any case, I complete each step for the whole picture before I proceed.
Roughing-in the picture involves laying in each section of the work in order to get the general value and hue for each major element. In cases where I have a dominant feature, such as a middle or foreground tree(s) or building(s), I, typically, rough-in these first so that I can be sure that I am pleased with their form before I take the time and effort to work on the rest of the picture. I also work from dark to light. That is, I lay in the dark areas before proceeding to the lighter areas. The dark areas control the balance, visual weight of the painting and are critical to creating a pleasing composition.
The Second Step - Primary Finishing
After roughing-in, I complete the painting, except possibly for some final details, by working from the darker to the light values. For instance, if painting snow that may have three values, I first paint the darkest area, the shadows, and then the light areas and, lastly, the brightest area when the sun may be reflecting.
The Third Step - Final Details
Certain works may call for some final details that are easiest when done on dry or tacky paint. These may include things such as glazing or adding very bright highlights.
A Final Note
It is very important to regularly stand back and view the painting from the distance at which it will most probably be viewed - typically, about 6 feet. Doing so helps to ensure that the work is developing as you wish and many times you will see things that were not planned but, in fact, are a great element to the work.