NOTE: This looks MUCH better in pencil, so I would suggest you draw it on paper.
First, sketch the top of the dragon's head-make sure to draw the horns!
Now the dragon's jaw. Try to make the teeth look quite sharp, it makes it look much more awesome.
Starting at the second horn, draw a few spikey scales, then another horn. From the new horn, start to draw a similarly spikey neck.
Sketch/draw the rest of the neck, making it look as if its turning its head. Add some detail to the horns.
Now, draw scales on the dragon's head.
Continue to draw scales all the way down its neck.
This part is a bit tricky and will probably take the longest. Take your pencil and shade the whole dragon, even its eye. As you may know already, you should shade darker in places that would naturally have shadows, like underneath the horns and its jaw.
You're dragon should now look something like this (but shaded). I hope you like it!