Since no one has actually seen a dragon, what a dragon looks like is strictly in the eyes of the beholder. For that reason, the art of drawing dragons is a popular one. Imagination rules!
But, if you're a little shy about starting from your imagination, others have blazed a path for you:
Hart, Christopher. Drawing Dragons and Those Who Hunt Them. [YA 743.87 HAR]
Masiello, Ralph. Ralph Masiello's Dragon Drawing Book. [J 743.6 MAS]
Peffer, Jessica. DragonArt: How to Draw Fantastic Dragons and Fantasy Creatures. [YA 743.87 PEF]
The Great Book of Dragon Patterns by Lora S. Irish [745.4 IRI] contains patterns that you can copy to use in any number of crafts projects. If you have a child who loves to color, you can photocopy some of the patterns and let the child loose with crayons and markers, sequins and glitter. Your child's imagination is limitless!