A screenplay averages 100 to 125 pages to tell a story within two hours. A novel can range between 50,000 and 100,000, words depending on the novelist and publisher. While a richer plot can emerge within a novel than a film, it is imperative as a writer to be concise in your language. As Mark Twain said, "use the right word, not its second cousin." This means that you should say exactly what you intend and no more. Adding what some term "fluff" within your story simply to meet a word count does not make a story better and often will detract from the flow of your plot. Show your audience what you want them to see, and nothing more.
Avoid giving all the information to your audience at one time. One of the elements shared by both novelists and screenwriters is the ability to keep an audience guessing as to what will happen next. Regardless of genre, a touch of suspense will engage your audience. Drop hints and clues as to what is coming and allow them to attempt to solve any mysteries, such as which character is really behind a given conflict or how the main character will manage to escape a dangerous trap. This suspense will give your audience the reward of a surprise at the climax of the plot.
Even if you write from the point of view of an anti-hero or antagonist, you must show elements of this character that can make your audience sympathize --- or even empathize --- with his perspective. Giving depth to a character helps capture the attention and imagination of your audience and bring them deeper into the story.
Write dialogue that both reveals the characters and their actions. Allow the flow of a conversation in a given setting and within a certain scenario to tell the audience what the characters are doing. Visualize the characters in the midst of their scene and imagine them as actors in a movie; determine what common motions a person would make when speaking the lines you have in mind. Decide whether the actions are common enough to be mentioned in descriptions and verbs, or if they can be either taken as a given or mentioned within the dialogue. For example, one character could say to the other, "Would you stop that incessant sniffling!" in the midst of a conversation. In this example, it becomes clear that the character yelling finds the constant sniffling of the other character distracting and frustrating. Neither of these needs to be described in the text.
Utilize the descriptive support of your novel's setting to help indicate what type of environment shapes the motivations of your characters. When describing your novel's world, think about the films you have seen where the camera pans a location when characters and dialogue are not currently the direct focus. Imagine your own world in the same way, panning your inner "camera" across the streets of your main character's hometown, or placing yourself at a high point to look out over the landscape. This will help you provide illuminating details to share with your readers and allow them the immersion necessary.