Layout Sketch (Draft)

It's a good idea to start with a Layout Sketch (or Draft Sketch), to get you started on drawing the real thing.

This step will help you get the proportions right.
Start with a grey Layout or Draft Sketch as shown.

Once you are satisfied with the grey Layout or Draft Sketch, draw over top of it with another color (black) to create your final drawing.  (I replaced the grey in the following picture with red to make it distinguishable from the black, although in practice the grey works well because it kind of blends in).

Then remove the grey from the final drawing.  (Use Color Replacer).
If you have no idea how to use Color Replacer, see A Few MS Paint Tips.

Congratulations, now you know the steps I use to create a basic cartoon drawing.