Draw a hill or slope.
Add another on top of that one. Make sure where the red arrow is is round, for its nose.
Now add the line for its mouth. Under that, add another line for the jaw. Notice this line goes up at the end, where the red arrow points.
Now add a bit more lines. You'll add the back of its neck/head, which will follow the edge of your paper. Now at the end of the jaw, add a line. A bit further over add another, for the end of its neck. These two will be the belly/underside part, as you probably know :P
Now bolden all of your lines, besides the one you first drew in the beginning. That one was only a marker. NOTE: You might think that line is pointless, but don't erase it yet!
You're done - the rest is up to you! If you are stuck, here are some ideas to add: Eye - Horns - Nostrils - Spikes - Belly lines - Color - Bold the lines. If you are still wondering why the line is there, you use it to draw where the spikes will be or where the center of his head is. If you want some more help or ideas, be free to PM me or comment. I'll be happy to help!
Using the steps, I drew this ^