Write well. Write often. Edit wisely.
Fiction can become real for readers. A look at how The Princess Bride combined narration with showing and captured not only a little boy’s attention, but the attention of a wide audience.
Scenes—someone doing something somewhere—are the pulse and images of the novel. Don’t skimp on scenes. Use exposition to connect them, but be sure you write them. Listening to a character’s thoughts, without knowing where and when he is, can make for dull reading.
Not all novels contain sex scenes, but for those that do, the sex needs to fit genre and character and plot. Learn what it takes to add sex to fiction.