I don't think I've actually ever seen a tutorial on this before, which is kinda sad.

I've been experimenting with this kind of recently though for fun, and I've gotten one successful sketch out of those attempts

The colored one is the successful one, and the sketch is a recent disaster I tried. 

(you/we also may see the red dragon appear more often in the future.)

If you're drawing the back of a dragon, or really anything, try more of a very rotated side drawing or a 5/6 view coming from the back.

1.  Draw circle, or any other shape, for head base

2. draw head, make sure the other, often unseen part of the head is more out than it would be

3. draw back of neck and rest of neck, draw the left/right side (other side than what you use, for example: I often draw dragons facing left, so I would make sure some of the right side shows)

4. Draw any details you want, and if you add horns, make sure the one farther back comes out a lot more

5. erase extra lines and finish any details

For any more detailed drawings like full body, look up the back of an animal you want to reference, like 'the back of a cat' or 'the back of (insert animal)'. 

And Have fun!