Novels are made up of scenes, or segments of the story. The average novel can contain anywhere from twenty to sixty scenes, depending on the author's style and creative choices. Every writer defines and writes scenes in their own way, so the way I put together a scene may not work for you. Feel free to adapt and interpret this information to best suit your writing style.
When I compose a scene, I consider what I think of as the five P's of scene-writing:
1. People: Who needs to be in this scene?
2. Place: Where does the scene happen?
3. Plot: What part of the plot is involved in this scene?
4. Progression: How will this scene move the story along?
5. Point: Does the scene serve the story?
I believe thinking through a scene before you write it helps prepare you for the task at hand. Even if you're an organic writer who hates to plan ahead, you can use these points as a sort of mental checklist while you're composing.
#1 & #2: Most writers do consider which characters to put in a scene and where the scene should take place; these are the most obvious building blocks. You have to know the players and where they are. The most frequent problems I see in novels are too many wall flower characters in a scene (they contribute only housekeeping-type dialogue, or just stand around and do nothing) and settings that are so overblown and overwritten that they eclipse the characters and everything that happens in the scene (aka travelogue writing.)
If you experience these problems, my advice is to 1) remove any character who does not serve a defined purpose in the scene, and 2) write your characters, dialogue and action first and your setting last.
#3: Every scene should tie into the plot in some way. If it doesn't, it's pointless filler, and nine times out of ten it's going to bore the reader. Don't try to save scenes like these -- get them out of your novel.
#4: Advancing the plot or moving the story along or whatever you want to call it has to happen, or the novel falls into the Sargasso Sea of Storytelling and goes nowhere (most often this takes place in the middle of the novel, when it's too soon to wrap things up, but too late to introduce new stuff for the reader.) I think the way to avoid novel lag time is to outline the plot a little more carefully before you write, but not everyone likes that approach. So think about adding a subplot or subplots that are resolved at different times during the story.
#5: There has to be a point to writing the scene, as in it does something for the story. Most often the pointless scenes I read are saturated with technobabble, infodumps or a dumptruckload of backstory that could have been better integrated into the story. A scene without a point is like yelling at the reader As You Know, Bob. . . . for five pages.
One scene-organizing trick I teach to my students is the 911 call. If you're not sure how to tackle what happens during a scene, take a tape recorder and dictate the scene as if you're calling 911, i.e.:
"Hello, operator? A huge fleet of alien ships just surrounded this planet. There's like three hundred of them. They're powering up their weapons. They're firing! Wait, they stopped. This guy in charge of the fleet is sending a signal to the surface. He's threatening to fire on the inhabitants if they don't turn over this doctor chick he's trying to capture. The doctor chick is negotiating her surrender. She won't let the people on the planet die protecting her. It really ticked off her ex, but the guy she loves now doesn't seem to care. What a jerk . . . "
How do you guys tackle scene-writing? Have you come up with or found any techniques that help? Let us know in comments.
Writing Scenes That Move Your Story Forward
Writing the Perfect Scene (link swiped from Simon Haynes's excellent page on How to Write a Novel
From a screenwriter's POV: John August's How to Write a Scene
How to Write a Great Combat Scene