A chapter needs a protagonist and an antagonist, as does any story. These may or may not be the protagonist and antagonist of the entire work, but there must be a conflict of some sort to keep the reader emotionally invested and interested. It may be a battle, a love scene, a betrayed trust, or even the final showdown. Any way you cut it, a chapter must contain the elements of a story, for it must have structure: a beginning, middle, and an end.

The protagonist of the chapter does not need to be a good guy, though if the story is about good versus evil, you may find it beneficial to write at least one chapter of the book with the good guy in mind. He may very well be a despicable, self-centered lout who sees things through his warped sense of morality. He could be an evil wizard, a rising politician, or drug dealer. What makes him the protagonist is his ownership of the arc of the story, whether the outcome is to his benefit or not. The antagonist doesn’t own the arc, but instead stands in opposition to the protagonist. You ask yourself, does this apply to various genres beside the obvious, like fantasy and science fiction? For mystery, it is the unseen and the hidden that plays the role of the antagonist, but it must be palpable and real to the reader. For suspense, it may be a mixture of the unseen mystery and a real individual or group who stands in opposition. For romance you may wonder, how can there be either, since it is the pairing or division of two or more love interests. Ah, there lies the greatest conflict of all -- and you have the protagonist and antagonist all present. Would it be anything more than pornography if the characters in the scene found it easy to come together? Maybe there is a husband or cuckolded king in the scene. Romeo and Juliet are fine examples of romance gone wrong and demonstrate the offstage antagonists as feuding families.

Another point I should make is that you needn’t stay within your genre for the chapter. A mystery can have chapter which is a romance, as long as your readers have come to expect this sort of thing from you. A science fiction can jump into fantasy, something which certain authors like Terry Goodkind have done very well. There are genres that are not compatible, but I will leave that as an exercise of common sense and decency to the writer. Remember that you warn the reader with foreshadowing that you may switch genres or they may not only put the book down but run shrieking out of the room. If you were writing a romance book, and introduced raw direct horror, for instance, your average romance reader may be just a little put off. Your agent may suggest reclassifying you novel when they start getting complaints in the mail.

The conflict is easier to imagine. We have conflicts every day of our lives. Change the stage and you can take any mundane conflict and turn it into an epic battle. How many times have you known a coworker who has taken credit for your work and you are helpless to oppose them? Transfer that motivation to the apprentice of the king’s magician and you have what could be the source of some fine conflict. A switched up potion or a faulty spell, and “shazam!” you have action!

As for structure, the beginning sets the stage for the drama to follow and prepares the reader for the yarn you are about to spin. It describes the players, builds the scene, and identifies the conflict. The middle is where the bulk of the action occurs. It contains the rising arc of the characters in the story and builds the tension to a crescendo. It may be as small as a single paragraph or as large as needed to grow the arc. It must take the protagonist somewhere physically, emotionally, mentally, or spiritually, that they weren’t before. It must also prepare them for the end of the scene. The end often is the hardest of all to write, but I have a little trick you might want to remember. Treat the ending like a link in a chain that connects one chapter to the next. It helps on occasion to skip the end of a chapter and write the next chapter’s beginning first and then come back and write the ending of the previous chapter. In some cases, you might want to write the beginning and ends of all of the chapters as a story in its own right, leaving out the fat and juicy middles. This is a very good practice, since it essentially yields the synopsis you will present to an agent and makes a fine instrument to construct a book.

Overall, keep in mind the arc of the book and motivations of your characters, large and small, important or insignificant, at the chapter level and in your book as whole, must agree in the end. If you neglect the motivations of these characters as they transform on their journey, the reader will neglect your book as well.