The opening scene of your novel should really be the opening scene. A novel is a sudden window opened to let us watch an arc of action from its initial to its closing phase. If you open the window too early, your readers have to drum their mental fingers waiting for the action to start. Open the window too late, and you'll find yourself desperately filling in with flashbacks and infodumps.

How do you know what action is the initial action? What is your story about? A young girl, suffocated by small-town life, deciding to head for the big city? Or a businessman at the end of his tether learning that, on top of everything else, he has cancer? Where do you start telling that story?

The temptation all too often is to begin by describing the people and setting for your readers, to soften us up so we'll understand the subsequent behaviour of your characters. Thus you have the young woman rant to a friend about the constrictions on her life, you show us the businessman's hectic treadmill existence for two dozen pages to make sure that we soak up its horror, in short, you spell everything out for us. You do this because you are anxious that we, the readers, won't understand, that we need to be conked over the head until we get it, that we are too narratively naïve to grasp what's going on unless it's counted out for us in baby language.

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