In beginning art classes you actually start with tracing. Take a photograph of the dog. Print it out, and then trace with tracing paper.
I know it sounds elementary, but what you are doing is actually strengthening the muscles in your hand.
After you try this a little while, start to draw the dog just by using the photograph. First start off and try to draw the dog with one line without removing the pencil from the paper. It is hard, will look a little funny, but it will help develop your abilities to distinguish shapes.
Every line drawing is made up of shapes and line, you might not really know it yet, because it's not the geometric shapes and lines we all know and love. You just have to train your eye and your hand to make sense of them.
Another way to help with this is to not make sense of what you are drawing. Borrow a kids coloring book, turn the page upside down, and draw the item on the page. Your brain will not make sense of what you are doing, but you are drawing the lines. Turn it upside down and you will realize you have copy of it.
You can also distinguish shapes better by squinting at your photograph. This helps make the contrast of light and dark more prevalent and allows you to see the "shapes."
Different dogs are going to require different "shapes" and lines, after all dogs are different shapes right? A toy poodle has a lot different shape than a greyhound whose torso is long and slender.
Anyone can draw, it's not about talent. It's about practice. I know because I have taken about 10 art studios at a 4 year university, and could only draw stick people at first.