Imagine an interesting person with a serious problem. Ideally this is a problem you know something about, if not, do some research. The problem ought to be something that people care about and can picture themselves facing, even if it takes place on another planet, or is set in a world where magic is mainstream. Your main character should be reasonably capable, empowered, and still have to fight with everything they’ve got, with no guarantee of success. The main character should be the person who has the most to lose, out of all your characters.
Your job is to make this character’s life horrible. I mean it. No matter what they do, their problems get worse and worse, and they find themselves in greater and greater danger. Maybe they start the day with a parking ticket, but by midafternoon they’re being questioned as a suspect in a murder trial. Their best isn’t good enough, and they are forced to dig deep, to think boldly, to make decisions they are uncomfortable with. The stakes should be incredibly high, and their fight should be against an antagonist who is believable and compelling.
Use tight language to keep your reader’s eye on the page. A straightforward, journalistic style is easy on the eyes and keeps the action humming. Choose bold verbs, and don’t gum up your prose with adverbs. Read your dialogue aloud to make sure it’s concise, and that it sounds right for that character in that moment.
Make your writing sing with sensory detail. Appeal to all of their senses, and as Karen Joy Fowler says, the reader has more than the five senses we talk about, they also have a sense of timing, a sense of justice, a sense of humor, a sense of taste.
Avoid generalizations. The reader doesn’t know this world, your job is to tell them, using specific details, what the world is like and who these people are. What exactly does your character notice about the world and people around them? What they notice tells us who they are, for example if a character always notices what people wear, we understand that fashion is important to them, or maybe socioeconomic status.
Keep a list of things that might go wrong, like the power goes out, there’s a car accident, or an unexpected phone call with bad news. Maybe the refrigerator stops working, or someone falls ill or goes missing, whatever makes sense for your novel. Whenever you get stuck and don’t know where to go next, check your list. I forget who originally came up with this advice, but it’s a fantastic way to jumpstart the plot.
Finally, think about what each character wants, and write them from that core. What motivates them? What do they fear? How hard are they willing to fight for what they want or need? What happens when they’re backed into a corner? What do they really, really care about? What’s the worst thing that can possibly happen to them? Know these things, and you’ll know who they are. A tight plot isn’t just bad things that happen to people, it’s mostly about who these people are, and what they’re willing to do to bring about resolutions.