You don't always want to spend hours on a drawing. Here's the process I use for quick sketching. Just because a drawing is quick, doesn't mean you have to only do an outline. By observing across the form and spotting the main areas of light, shade and texture, you can create an effective three-dimensional sketch.
I'm using a reference photo to work from so that you can see exactly what I'm looking at as I draw. I'd use the same process to sketch from life, if the dog will sit still long enough! I wouldn't normally choose such a front-on image either - a three-quarter view is much easier to model. But front-on portraits are popular, and its a pretty cute shot, so I'll use this as an example.
Not what you're looking for? For a beautifully textured but realist approach to graphite and charcoal drawing, try this lesson on How to Draw a Wolf by guest artist Michael Hames, or this realist Draw a Wolf in Colored Pencil lesson by Janet Griffin-Scott. Both of these lessons adapt easily to using your own dog image as a subject, following the steps demonstrated.