Perhaps you have an art class and in it you are required to make a painting of a cat. This can be a challenging problem. A cat's fur can be a complex range of colours and textures that is difficult for the novice to capture in paint. Getting the proportions of the head, body and legs correct is a painstaking process. If you're working from a live model it's difficult to make your feline subject stay still long enough to create a good likeness of him.
Stretch your watercolour paper by soaking it in a tub of clean water for about 15 minutes. Remove the paper from the tub and lay it on a flat, smooth board--preferably a sheet of heavy Masonite or something similar. Fasten the edges of your paper to the board with gummed tape, which you can buy in an art supply store. Allow the paper to dry--this may take 24 hours. When it is bone dry, your paper should be flush to the board's surface and will not have any wrinkles.
Lay out your palette of watercolours. If you are using a tray of cake watercolours, the work is already done for you. Group colours on your palette by temperature---reds, oranges and certain earth tones, such as burnt umber and raw sienna, are warm colours, while blues and greens are cool colours. This will make colour mixing less complicated when you begin to paint.
Sketch your cat with a pencil on drawing paper. You can work from life, drawing the feline while it naps, if you don't mind having the cat move occasionally and ruin your pose. For others, a good photo of a cat can be equally good source material. Study the proportions of the head to the body and sketch both as rounded shapes first. Observe the angles of the eyes, ears and mouth and gradually add more detail to your drawing. Sketch in the texture of the fur and the tail.
Paint a thin wash of watercolour onto your paper by choosing a neutral tone to begin with--say, raw umber--and loading your brush with water. Dilute a tiny bit of paint with your wet brush and paint the cat's body and head with the large shapes that you began your drawing with. When your initial washes are dry, choose secondary colours that will be your darkest tone and use it to distinguish details in your painting. Use a little paint in the areas that will be the lightest. With watercolour, you will need to let the white of the paper show through highlighted areas. Choose your middle tone---the ones between the darkest and lightest tones---and fill them in. You will be well on your way toward completing your cat painting.