This example I am going to use a photograph. It is a good idea to take lots of photographs before you start painting trying out different similar compositions to get one that you like think is balanced and will work for you like a painting. Don't want to have anything that is too big and complicated, nor do you want to many details. Make sure there is something which can be a clear focal point and that there are other elements which describe mid-ground in the background. Try to avoid too much foreshortening as this will make life much more difficult than it needs to be.
To begin with, make a quick line drawing as lesson time getting this accurate and in proportion. Kissing the drawing right is essential since if you don't, your picture will always look awkward or out of proportion. The mistakes maybe drawing are immediately noticeable. If you can, use a projector trace over the image with a simple line drawing. That is why have done in this example. It is always better to work from real life, however, it is easier to work from a photograph which has already been translated into two dimensions for you.
Once you have completed the line drawing, work in one colour to create some underpainting. This first colour will help you unify the picture make sure that everything relates in part of the image.p in this example I am using blue for underpainting. Blue is a good choice because it is the cold colour stop most people tend to paint naturally with hot colours, and, very often, when first starting to paint there is a temptation to just use dark brown mixed with white throughout the picture. This will lead to a hot, dry, muddy monochrome. Ideally, we would avoid this kind of flattened hot colour, so we use cool colour as an underpinning framework.
Because this is underpainting, you can use a brush or a sponge or a rag with quickness and immediacy. Build the blue up and make it darker why you have darker areas and tones in your picture. Do not worry about making the underpainting very accurate because it will largely be obscured by the colours and over the top of it.
An easy way to think of this blue layer is that it is for you, rather than for the other people who will look at your picture. This blue layer will help you in building the picture.
Once you have completed the blue layer, you can add some dark warm brown in the shadow tones. By having the blue underneath, and then adding brown above it, you will begin to balance the picture and avoid it being a flat monochrome (monochrome means "one colour").
At this point, you should be applying thin and sloppy wet paint. You could use a sponge get this done quickly, you could use a large brush, just make sure that your paint is loose and thin. You do not want the paint to have any thickness at this point. You will be applying more layers over this one and in general, when working on a painting, you should always progress in layers from thin paint to thicker paint as you develop the painting.
Having applied dark brown colour, typically, a burnt or even raw umber colour, you can add cut out for the mid tone. It is a good idea to use green colour the mid-tone since it is not generally hot or cold but neutral and can float somewhat if brushed in thick layers. Make sure that you of rushing or sponging this green colour in light do not overpaint too much of the underlying colours. At this point, your colours should merge together work with each other.
Having completed the mid-tone with the green colour, you can add some red accents to your picture generally around the highlighted areas but also throughout the picture to make it balance. The rules I am suggesting here on loose and should be applied as a general guide rather than a fixed and concrete exact formulation. We are using colours to match the tones of the image but also, responding to the unique image every time.
The goal of this kind of underpainting is to completely cover the image all over and create one unified vision, one world in which all the parts of the picture exist and inter-relate. Essentially, this will help us avoid painting unrelated individual items that lacked cohesion and a continuous space.
Now the local colour is added to the picture. The focal point of the spout of the green teapot is chosen. Everything will be made to be more blurry and less finished and less detailed the further it is in space from this focal point.
Notice how there are still nop sharp lines between any of the objects in the painting.
The thin black lines have been removed - this image was made on an iPad - the lines were on another layer which was turned off. When you paint in the real world, you would paint over your original guiding pencil lines and they would have been obscured completely along time back in the process.
Now colour details can be added to resolve the solidity of the shapes and make them appear to exist in space - remember, it is crucial that painting is brought up in levels of finish all lover so that the painting is balanced but, at a certain point only those parts nearest to the focal point can be resolved fully.
At this point, the picture has been more developed so that the rim of the jug in the background is shown and some rough highlights have been added. The spout of the teapot is the most resolved part of the picture and the lid of the teapot is more defined so that the roundness and solidity of the form is made more concrete and real.
This picture could be worked up further until it was finished to a much higher level of detail but it could also be left at this point so that it has a loose, immediate and fresh, spontaneous feeling.