So you’re writing a series, say the third volume, just to pull something totally at random and in which in no way applies to me. How do you approach prewriting when you’re looking not just at the book alone, but also in its place in the series?

Well, in my dad’s favorite answer to almost any question: it depends.

First off, what kind of series are you writing? Is it the episodic sort in which can go on more or less forever and which a reader can more or less start at any point and easily pick it up? Or is it a closed, serialized story with a clear beginning, middle, and eventual endpoint? Each series type faces a critical issue of balance, but in different ways.

For an episodic series, each entry is a standalone story following (usually) the same protagonist. For obvious reasons, this style lends itself well to procedural-style stories (crimes that need solving or medical cases that … also need solving).

Any series of this sort, one with no planned ending, is operating on a ticking clock. There are only so many stories that are worth writing for a given series. The longer it runs, the more likely installments will begin feeling like retreads. This is doubly dangerous for a series of novels with one writer, who is going to have their own tendencies and blind spots and, unless their name is China Mieville, will eventually start to fall into the same story ruts given the same story ingredients.

That being said, one surefire way to shorten your clock is to break the key elements that make your series work in the first place. Whether it’s author boredom or fear of getting stuck in a rut, I’m talking about change for the sake of change.

To look at this from a television perspective, The X-Files really began to fall apart as a series when David Duchovney’s Mulder left the show (followed eventually by Gillian Anderon’s Scully). At that point, two entirely new characters, Agents Doggett and Reyes, became the show’s new leads. And honestly, they were fine in the roles. If the show had begun with them as the leads, it might have found its own kind of success. But readers had been tuning in for years to watch Mulder and Scully battle the paranormal and their own repressed feelings for one another. In this case, the actors wanted out, and the showrunners can’t be blamed for that. But writers would do well to take note. It’s important to have a good sense of your series’ sine qua non, that which it cannot exist without. Remove or change the central dynamic that makes your series appealing at your peril.

A serialized story with a planned beginning, middle, and end faces different balance challenges. Each volume needs not just to be an entry in a larger narrative, but also to tell a satisfying story in its own right. This requires more work on the author’s part than in our episodic series, where each story is more or less standalone with the same characters and/or settings.

But because our story is fulfilling double-duty, it also has to be a part of a larger narrative (both in terms of plot and character), and that means treating the entire series as one enormous story, with its own sense of rising action and stakes. And this leads us to the great danger of the serialized story: the all-consuming desire to top what has come before. It’s very easy to fall into this trap, to look at each installment as needing to be somehow bigger, with higher stakes, and wind up with a story that is more ridiculous than thrilling. It’s a good idea to approach this sort of series with an idea of what you wish your final conflict in your final volume to be. This allows you to calibrate the individual conflicts driving the individual series entries and make sure you aren’t peaking too early.

Fiction of all sorts is rife with examples of this, particularly with bad guys that are all but unkillable in the first installment and become mere cannon fodder by the final entry. The Wheel of Time makes Rand al’Thor’s first kill of a villainous trolloc an epic struggle in which he nearly dies. By the end of the series, trollocs are less effective than imperial stormtroopers at menacing our heroes. That’s okay in this instance, because Robert Jordan effectively shows the reader how Rand and his friends learn to become bigger and bigger bad-asses in a believable progression. It doesn’t wreck our suspension of disbelief because Jordan puts in the work.

By contrast, when Star Trek: The Next Generation introduces the borg, they are a terrifying and all-but-invincible foe. Two series later, in Star Trek: Voyager, the drive to increase series ratings brings the borg back on a regular basis. Where previously a single borg ship was able to obliterate entire fleets of starships, now the Voyager successfully contends with the borg week-in and week-out. The villains are robbed of their menace.

Writing a series adds several dimensions of difficulty to your job. It means having to keep multiple books in mind at once, both ones that have come before and ones you haven’t written yet. But no matter which kind you are writing, a little thought and planning ahead of time can save you a lot of pain (and painful rewrites) down the road.