These rules apply to everyone(aka common sense):
First rule on fan fiction: Don't write it. Seriously, if you're a gifted writer, make something original, something that's your own. Making fanfics just kills creativity(subjective, but still...) and if you just plain suck at writing, the ffort would be better spent on something else.
Second rule: If you do decide to write it, and expect someone to read it; keep it civil. No matter if it's the ending you wanted but did not get or your view on the story, write about the characters, your or the game's, not your very own private fantasies of the characters or buried urges. That's not only sad, but also very annoying to read, insulting to the public plus you'd be better off seeking help.
Third rule: Give respect where it's due. People do think, no matter what they tell you in the internets, so make them do so. Even though your public might seem to love what you're spewing out; stop to think. They're most likely as sad as you, hormone-crazed fanboiis or poor fangrrrls, or(this one being the worst) just polite. Akward politeness, with the obligatory smilies, is a sign you're doing something wrong. IF you've gone so far as to break first and second rule, then you might as well do it with style and give it your best shot. The only thing you might offend is your psyche. The readers that matter are long gone by then anyway. And now once you're at it; you might as well read the final rule.
Fourth and final rule: The fiction is ready, you know how to spread it, it's the final draft and everything seems fine and dandy? What're you waiting for then? Uploa...oh no. Proofread it first. Spell check. And kill off inconsistencies. If at all possible, get somebody to read it before posting for all to see. A second view on things never hurts.
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