Emphasis on the BAD
. Now, I don't have anything against slash as a genre. Done properly, it can be just as enjoyable to read as hetfic. What I hate is when people misuse the genre. Remember how in 3.
I talked about bad pairings? Badslash is full of them. I once talked to another Naruto fan about character assassination in Naruto badslash. Her favourite character Deidara was a frequent victim of this; for some reason or another, a lot of badslash authors like to turn him into what is basically a girl with an XY chromosome.
I've seen badslash in the Streetfighter fandom do this too with certain characters; Vega is one of them. Look, the guy likes to perform assassinations, cagefight and kill bulls in his spare time. He's also hardly a girl, figurewise. If you're going to make a male partner in a slashfic a girl, then you should really consider ditching slash and writing hetfic instead. Also, when you're writing slashfic, there is no need whatsoever to either vanish all the girls inexplicably, or alternatively to turn them into nasty jealous harpies.
7. Purple prose.
This does not refer to descriptive text; there is a difference. No-one is saying that you should only write in dull or humdrum text, but you can be descriptive without lapsing into sick making flowery text. Purple prose is so over extravagant, ornate, or flowery as to break the flow and draw attention to itself. It is sensually evocative beyond the requirements of its context. It also refers to writing that employs certain rhetorical effects such as exaggerated emotion to force the reader to think a certain way.
Here's a link
that gives examples of purple prose and when descriptive text goes too far.
8. Lack of consistancy.
If you're writing fanfic, then for the love of cheese, stick by the rules that the author has laid down. For example, in the Harry Potter fandom, there are far too many badfics where the author has her disgusting self insert be an American exchange student. America more than likely has its own magic schools, a canon example being the Salem Witches Institute.
Don't introduce creatures that don't exist in canon, for example adding in elves to Harry Potter and fairies to Lord Of The Rings. Don't, for god's sake, introduce technology to Middle Earth. And finally, don't tag on extra siblings that have no reason to exist at all, other than as a vehicle for your Mary Sue. That's just lazy writing. Arwen doesn't have a sister. Nor does Sasuke, who's entire family save Itachi was killed if you bothered paying attention.
9. Author notes.
Especially if said author notes are shoved randomly in the story, breaking up the text and serving no purpose whatsover. If you must, then post an introduction at the start, before your story starts. Don't use it as a means to randomly post about how much you love your fans, have inane conversations with either yourself, your characters or imaginary people, or explain things like plot elements that you ought to have done so in the story.
Also, don't use author notes to essentially say, "shut up haterz!1!eleventy! Rowanna Mystick Angle Demetor is NOT a Mary Sue!1! Your just jelus!1" It doesn't help your case, and just makes you look extremely immature. If, in your reviews, someone has posted constructive criticism, then read it and thank the reviewer for bothering to give one. Take the advice on board; if you know anything about writing, you should be able to tell if your character is starting to veer towards Suedom, and stop it.
10. Mpreg fics.
Unless it's canon that it can actually happen I think it should just be left the hell alone. There isn't anything funny or romantic about it, and a lot of badfic authors seem incapable of writing mpreg in a way that doesn't insult women. A lot of mpreg is also incredibly sexist and misogynist; if women exist in the fic, they're generally written as being nasty horrible people who shouldn't be around.
The biology aspect is what gets me the most tho. Science bit: men can't get pregnant. They don't have the necessary equipment to do so. They also won't magically grow a uterus and birth canal when needed. If you want your slash pairing to have children, then either they can adopt, or you'll have to have a woman involved to act as surrogate. Honestly, I've read a lot of mpreg and still the only plausible mpreg story I've read is the Norse myth about Loki and Svaldifari.