Filing Off the Serial Numbers
Many of us have been in the position of having written fanfiction. Hell, I think most of the author populating the M/M-gay romance genre got their start in fanfiction. And, at times, we have looked at the 80,000 word novel we wrote for our particular fandom, seen almost nothing of the source material in the work, and decided… hell, why not turn it into an original manuscript and make some money off the hard work we did?
Well, because it's not that easy. I can't tell you the number of books I've picked up that are barely more than poor disguised fanfiction. From Star Wars to Lord of the Rings to Sherlock Holmes, it's depressing. And the fact that publishers are publishing it! Now, I've seen people say that some publishers might not be wholly familiar with those fandoms or source material, but I say, come on. I've never read Sherlock Holmes and only have the vaguest introduction to Star Wars, but I can see a fanfic when I read it. A mass search and replace with names and places does not equal filing off the serial numbers.
Let's start with the simplest issue: Fanfiction is paced differently than professional fiction. It's true. It's why you can see 'Chapter 143 of ????' attached to a fanfic. Authors can just ramble. They don't know what's really important for a reader versus what they simply want to write. Now, the two are not mutually exclusive, but for the most part? Fanfiction is windy. Plot holes abound, and there seems no end of 'twists' an author can weave in.
The second issue? Characterization. Or, actually, the lack thereof. In fanfiction, you have the source material as well as fanon to fill in most of your characterization and worldbuilding gaps. Authors don't have to think about where to put Aragorn or how he would react to something, Tolkien has already done that for them. This leads to weak characters and squirrely worldbuilding, and it's usually a tell-tale sign that someone hasn't put the work in to file off the serial numbers.
Third issue tends to be plot related. Many fanfics depend on the core plot elements of the source material, or made up elements based on the source material. This can make things exceedingly difficult when you want turn it into something original. When the original story is so entrenched in the fabric of the original world the author borrowed from, changing it enough to be different and original can be impossible without extensive rewrites. And, by that point, why not start from scratch anyway and begin something new and wholly yours?
But, in the end, sometimes we want to take that story we did put so much time and effort in, alter it, and share it with a larger audience for pay. Nothing wrong with that, but you need to keep those three main issues in mind when you approach that old fanfic and dust it off. Not to mention the very good chance that your writing voice itself may have changed since you wrote it.
Revision is not the word for what needs to be done. Rewrite is. If you have a 25,000 word fanfic to offer, it better end up as a 50,000 word category novel. You should add a significant amount of new material to make up for the lacking of source material. Worldbuilding, characterization, plot, and relationships all need to be approached with a fresh eye and a strong red pen. Don't just mass replace the names. Sit down and think about those characters. Who are they? What drives them? What are the fighting for or against? What is their motivation to go from who they are in the beginning of the story to who they should become by the end? All questions you should be able to answer—in detail—about these characters once you pull their from their source material.
The world. What about the world? What is it? Where is it? How does it look? What is its structure? What races live in that world? What are the political ties of those races? The questions are endless, and you should think about them in depth before taking on the challenge of reworking a fanfic. The world needs to be as original and alive as the characters. Yes, there can be some ties to the source material—taking your medieval elves out of Tolkien's Middle-Earth, but keeping the medieval aspect and placing them in your own world—but you need to be careful. The broader themes are fine, as the world only has about five plots, but the finer points—how Fëanor was the King of the Noldor and led their rebellion against the Valar—need to be altered completely. Don't make Fëanor into Fyner, King of the Spider Elves or some such thing and change nothing about Fyner himself and the world he influenced.
Have I filed off the serial numbers? Yep. What began as a filing off of serial numbers turned into a three year long creation of a world, creatures, religion, gods, afterlife, and characters. And I'm doing it again, only applying a half-complete fanfic to a world I created two years ago and playing with the past of that world. But it's hard work, and whether or not I am successful will depend on editing and the reception the various stories receive from my audience.
In the end, I hope I've done well. I hope I took the kernel of idea I had begun to wrap in fanfiction and created gorgeous and rich stories people will love instead of scorn as recognizable ripoffs. (Which, btw, they aren't ripoffs as I'm, by no means, trying to recreate the source material I originally fell in love with. >.> Just sayin'.) I want my characters to be my characters, and deep down, they are, as they bear no resemblance to their source material counterparts.
If you're going to file off the serial numbers, do it right, do it well. Make the stories and characters your own. Stop looking over into the other sandbox and just build your castle in your own. 
It can be done. You just need the fortitude and support to ensure it's done right.
