Read the next episode of “So, You’re A Cartoonist?” here: [link]
They say that the signs of being a good writer is when your characters start to do things which are totally unexpected even to you. However this can have negative effects too. Often I have a plan of where I want my main overall story to go, but then find that when I begin writing my characters have other plans. It can be fun to let your characters go off on random tangents, but you must never lose sight of the ultimate goal. One trick I've found which helps me stay focused is to restrict my chapters to a set number of pages.