The very first step of painting is choosing a good picture. I highly recommend using a good picture with good light in it. For example, this picture has beautiful light:
Another thing to consider when you're first beginning a painting, is composition. It's usually best to put the subject in one of the four corner quadrants of the picture, not right in the middle of the painting. Making things a little off balance by moving the subject out of the center of your paper will add interest. Sometimes, the center of interest may be the eye of the animal, and even though part of the face may be in the center of the picture, this can still work well. For example, in the picture below, the cats face falls right in the middle of the painting. But the center of interest, the eyes are right and above of center, and makes this painting work.
Once you have selected your picture, you can either draw it on your paper (I recommend 190 lb arches cold pressed paper) or trace it on using either a light box or the light through a window, a print out of the picture, and your watercolor paper. After you have transferred your drawing to your paper, whether you draw it or trace it on, you will want to use mask to save the most important small areas of whites, like whiskers or a glint in the eye. Here are two videos that show you a little bit more about mask and how to work with it.
The following video provides a little tip on how to keep your brushes from getting ruined from mask.
The next step, which you can do before or after you use mask (and you may decide not to use mask), is to tape down your paper...That will be the next post!