Regarding the length of paragraphs--size, or perhaps better stated, length, is entirely up to the individual author. Many of us like to write the way we enjoy reading. Personally, I like short chapters, particularly when I know I don't have a huge block of time to read. I can get several chapters read and not have to stop in the middle of a scene.
How does a writer know when to end a chapter? There is no acceptable template to follow. I've seen books that have fifty or more pages to a chapter; I've also read books with a one-page chapter. It all depends on content and direction. Ending a chapter on a suspenseful note, causing the reader to wonder what happens next, is a great way to end. But to use that same tactic for each chapter is to overdue it and diminish the use of a great writing technique. Some chapters may be necessarily longer in length to resolve a conflict or create a back story, while others may be shorter to illustrate a point, or simply be informative for the reader.
On one discussion board, I heard a very cogent argument for short chapters. The participant explained his preference for short chapters by saying he compares long chapters to listening to a talkative person. The individual wants to tell you something, but rambles on until it all becomes boring and tiresome. Keep the reader in mind when you consider chapter length--it's up to you, the writer.
