I found, that encouraging Santino to draw is much easier, when I give him a project, a task and then explain how to do it. Maybe he is not as creative at this moment to enjoy scribbling random lines and zigzags, but he definitely gets more excited and tries to draw after he knows exactly what to do.
I instruct him how to draw a dinosaur: a head, a neck, a body, 4 legs, a tail, eyes, jaws. He is pretty good in putting everything where it is supposed to be. He is not very elaborate on what those parts look, but yay! he draws them!
Here's a dragon, drawn following the same formula: a head, a neck, a body, legs (2 legs), a tail, wings, eyes. We read an online book recently about drawing dragons with eyes, so eyes became a rather important part of our art. A big, big step in this one: multiple colors! For the first time in a long long time.
I have a book, that instructs how to draw some objects or animals and we tried to draw something out of it. Rocket sounded interesting. We followed all the steps, decorated, and voila! A rocket! With stars and planets around. Do you see Saturn?
So my conclusion: don't get discouraged, if your little one doesn't show much interest in drawing or talent. Just give them what to draw, tell how and you might be amazed of what they are capable of.