There are no hard rules when it comes to art. However, there are principles that form the basic building blocks for all the visual arts and principles that guide an artist when they are composing a piece. These are often called "principles of art" and "principles of design." These vary only slightly from person to person.
My question to you is two fold: Do comics have basic principles? If they do, what (in your opinion) are they?
Most comic books that teach you to draw only focus on one style, rather than teaching you how to create comics in your own style. I hope to someday make a course on drawing comics that looks past styles and teaches core principles that anybody drawing comics would find useful.
I guess there's really two parts. There's developing your own style, which just takes a bunch of time and drawing. (including a lot of drawing other people's styles and random styles and experimenting and deciding how you want to draw ears and so forth.)
Then there's cartooning, being the merging of art and writing. Or it could be thought of as: your style is how you draw a picture, cartooning is how you combine the pictures into a story.
A couple of cartooning principles that come to mind:
-using space to convey time/manage the timing of jokes
-clarity of panel flow (if the reader has to think what panel/text bubble to read next, you've made a mistake)
Have you read Making Comics by Scott McCloud? Also Understanding Comics and Reinventing Comics. McCloud's works are the only widely-available and well-respected resources that most comic artists look to for standards and principles in sequential narrative storytelling (his phrase)