I definitely agree with Toby_Morpheus, it's excellent advice.
I would also say, if you really want to get into it haha, strip both dog and human anatomy down to some basics. Look at the shapes each create then see where they overlap. An excellent exercise in finding shapes is to draw over pictures of humans and dogs, once again just break them down to squares and circles and triangles etc.
Ergo Josh on youtube has a good example of this technique used on a Disney character