Dragons are incredibly cool things to draw, and can be quite challenging! What most artists do is to choose a real animal to base their dragons on, usually one of the following: horses, birds and dogs.
Then they study the skeleton and skull of the chosen animal and adapt it to become a dragon - add wings coming out of the shoulder blades, change the proportions slightly, that sort of thing.
Check out the Blast Art Showcase for inspiration. Hope that helps!