Sketching dragons is a fun thing to do, especially when you've practiced drawing dragons for a few years like me. And there are many dragon ideas that you can use, from Japanese dragons to Chinese dragons to your own custom dragon creatures.
Of course dragons don't exist in the real world so we have to rely on drawing them from imagination, but there are a few animals in the world that resemble dragons slightly and it's these that you can draw inspiration from, such as lizards, ,crocodiles, snakes and some other amphibious creatures, mainly for some of the general physiology of legs and arms, aswell as scaly skin.
Below there is a quick drawing video in which I explore a possible dragon sketch, of course it isn't perfect, but the intitial sketch never usually is, it's more on seeing how to approach a dragon drawing and work out what mistakes you need to correct later on in the drawing stage, so in the drawing video I just sketch a rough drawing of a dragon, nothing final, nothing finished, it's just an example of a sketch of a dragon.
Sketching is what you should be getting used to and finding out for yourself, pencil lines all come together to make a drawing complete and one idea can form the basis of several ideas, try sketching today.
Watch the drawing video lesson for some dragon sketching inspiration.
Also see - Drawing a Dragons Head