E.J Sue’s “Mechaforce” is one of the few “How to Draw” books I would point newbies looking to get into drawing robots to. It emphasises knowing the basics (Very difficult to draw a robot properly if you can’t use perspective) and fundamental shapes and even arm techniques, and gives a neat insight into how mechanical forms work in art.
These are just a few of the examples from the anatomy section of the book. It’s currently on sale on Amazon and worth checking out, though I will note it is not a “be all end all” resource, thankfully you can fill in your knowledge gaps elsewhere.
Key and Teeth 