Introduce your main characters and themes in the first third of your novel. If you are writing a plot-driven genre novel make sure all your major themes/plot elements are introduced in the first third, which you can call the introduction. Develop your themes and characters in your second third, the development. Resolve your themes, mysteries and so on in the final third, the resolution.
Michael MoorcockElric knew that everything that existed had its opposite. In danger he might find peace. And yet, of course, in peace there was danger. Being an imperfect creature in an imperfect world he would always know paradox. And that was why in paradox there was always a kind of truth. That was why philosophers and soothsayers flourished. In a perfect world there would be no place for them. In an imperfect world the mysteries were always without solution and that was why there was always a great choice of solutions.
Michael Moorcock