Okay, I didn't even know that "FanFiction" existed, before AUGUST of THIS year. When I did discover it, though, I actually enjoyed it very much, because I LOVED the idea that the fans of a certain work of Fiction could put there own imaginations to work in a work of friction that they love (so long as they use a PROPER disclaimer). I loved the idea of this, because, fiction, and/or, fantasy is, and/or, are, specific forms of entertainment that takes one to a great place, a place where that person's wildest dreams can come true, without the fear of being harmed. Knowing these fact, I went forth, and I under-went a SERIOUS/INTENSE session of FanFiction reading, from a CRAP-TON of Fandoms! After reading MANY Fics, from many Fandomds (I read pretty fast), I had decided that I had liked a good bit, but, I realized that quite a number of them were, ...Well, ...TERRIBLE. After realizing this, I settled on a FEW Fandom-Section, On FF.Net, that I thought, had the FEWEST mistakes, and/or, "crappyness." One of these sections was the JN section (what REALLY amde me pay-attention to this section, was, the LONG-ASS--SERIOUSLY, accroding to Google, it was a s LOONG as a J.K Rowling Book--Fic, Mara'a TOSOT, and I was all-like,: "
Wow, People HERE MUST be DEDICATED!"). Now, I am a VERY TOLERANT person, and, as such, I tend to try my BEST to leave a review (II--BIIIIG IF--I review a Fic, AT ALL) that can HELP the writer (constructive criticism). Usually, when I come a cross a Fic that I do NOT like, I won;t even give it the time of--like y mother always told me,: "If you don't have anything nice to say, then just sit there, and stare at the person with EXTREME malice written all over your face." ...And, so, that's what I do. HOWEVER, even though, I am VERY tolerant, and/or, understanding, I DO have a few things that will turn-me-off to a Fic.
Some of those things include,:
- Poor Sentence Structure, OR, A Terrible Use, And/or, Understanding Of The Language That The Author Is Using (I'm Multi-Lingual, And, Thus, I Can, And Do, Read In MORE THAN English)
- Unrealistic Chracter Actions, And/or, Traits, OOC-Ness In General (Unless There Is An AMAZING Plot-Point To Explain It)
- Terrible Spelling, OR, Terrible Grammar (In ANY Language--Although english Is Probabaly The HARDEST)
- Mary Sues
- Gary Stus (Redundant, I KNOW--But, I Just HATE These Kinds Of Characters)
- PWP (I Mean, Come-On, It IS A Fic, Based-On , A CHILDREN'S Cartoon!)!
- Reatrded Sexual Material (By Retarded--Well, I Think That You Know What I Mean)
- Leaving Carl Out Of Fic (C'Mon! He Is An Important Part, And/or, Character Of The Show Too!)!
- Killing-Off A MAIN Character, WITHOUT Good Reason
- A/N (Author's Notes), That Are LONGER Than The Damn Chapter (You ALL Know What I Mean!)!
- Vilifying Characters Unnecessarily
I'm pretty picky when it comes to fan fiction. If any contain any of these I won't even read it.
1. Character being OOC
2. Horrible grammar/spelling
3. Misspelling of character name
4. For the most part, any OC's- esp. making a character pairing with one (stupid IMO)
5. Pointless and/or crappy sex scene
6. Overly fluffy/romantic- I like substance
7. AU
Yeah, super picky like I said. Now your turn! 
Pretty much everything you said except the last two. 
-I cannot STAND when people spell the names of characters in their OWN FANDOM incorrectly. I mean, it just makes you think "Damn, why are you even here?" 
-Most OC's I am not a fan of. I pretty much avoid any fic labelled "OC" like the plague. The are rare exceptions, though. I read one good one where Eustace Strytch was paired with a male OC, for example.
-Characters being OOC - I especially hate it when authors superimpose their own hobbies onto canon characters. Like, I read a fic once that had Jimmy, Sheen and Carl (AND AN OC WHICH I DID NOT LIKE) setting up a metal band. The dude who wrote it wasn't a bad writer, but it was just so very OOC (IMO) that I couldn't take it seriously. I mean, Carl? Listening to Metallica?
I'm sure I can think of more later, but these are the immediate ones that spring to mind. 
EDIT: Ooh, I just remembered. I hate, hate, HATE when people use the word 'orbs' to describe eyes. (e.g. "He looked into her emerald orbs") It is my least favourite description for anyone to use in any piece of writing ever. 
I don't know why. It's just...AWFUL. It NEVER works. I wish people would just stop using it. 
Oh boy. I can't stand the "orbs" thing either. The English language definitely needs to come up with some more synonyms for "eyes".
Anyway, in addition to shitty writing, here are some of my Fanfiction deal-breakers:
1) Crossovers. I hate them. Even when the bridge between series is justified through believable plot elements, there's just something about the whole concept that really irks me. The only exception I can think of is where you take the cast of one show and put them in the world of another, but in a different time period and without any contact between the two original casts. An example would be kumorininja's idea for JN in the avatarverse, which I briefly summarized here: [link]
2) What I like to affectionately call "emo stories". I'm sure you've all come across these in your reading experiences: fics that are as intentionally gloomy and depressing as possible, with no redemption in sight and no solution for the main conflict(s) of the story. Bonus points if the story ends in a single or double suicide. 
3) I can't stand fanfics that kill off one member of an established couple so that the author can pair the remaining person with some other character. For the most part I don't like non-canon pairings between main characters anyway, though I don't mind when writers mix and match background characters. I think this ties into the whole OOC-thing everyone else has been talking about... good fan fiction is a continuation of and expansion on a series, not a radical departure from it. If you really want to tell a story that different, just write something original. 
4) I have no problem with mature content, even with teen fandoms (honestly - did you ever take a look around at the dirty stuff going on in your high school? That's life, people). However, it has to be handled with a lot of care, which is something most fan fiction writers are seemingly incapable of doing. I have no problem with well-written and plot-relevant "mature scenes", but the writing focus needs to be on the emotional and the experiential, not on the mechanical (i.e. what the characters are feeling and thinking, not what they're doing). As soon as you start giving me descriptions about "his throbbing manhood", you've turned your fic into unimaginative porn, and I'm no longer interested.
5) Song-fics. Sorry to people who like these, but I find it immensely unoriginal when an author just copies and pastes lyrics from some song and then "elaborates" to show how it fits a certain couple. If you really think that a piece of music represents certain characters from a TV show, make a music video about it. Jeez.
6) OCs who either a) overshadow all the cast members from the original show, or b ) are introduced with the sole purpose of being paired with the main character. I have no problem with OCs who are in a relationship with a more minor character, especially when that character does not have a pre-existing canon love interest.
For the most part I actually don't like reading fanfiction, because you have to wade through so much crap before you find anything decent. 
~*Mara*~ = ^.^ =
I'd agree with ALL of you, EXCEPT where you said AU (if it is done CORRECTLY, then it is pretty cool), fluff (it can be CUTE--SOMETIMES), and OC's.
I'm going to defend [SOME] OC's here. YES, I KNOW that [A LOT] of OC's are TERRIBLE, and/or, are Mary Sues, and/or, serve NO plot point, and/or STEAL the "spotlight," from the main characters, serve ONLY to insert the author (unnecessarily) into the story, OR, to be paired with another CANNON character. The above-mentioned types of OC's should be AVOIDED, and/or, not put into stories. I would DEFINITELY AGREE with THAT. HOWEVER!,: ...
...OC's that the author spent NUMEROUS HOURS creating, with the SOLE INTENTION of putting them into their FanFic, WITHOUT taking the "spotlight," from the MAIN CANNON characters, and who ONLY serve to further the story and are there as PLOT POINTS should be ADMIRED, and/or, EMBRACED! These characters, more often than not, DO have flaws, and, as such, are NOT perfect little "Mary Sues." Characters such as this include Mara's FUTURE cast, form "
TOSOT." THESE charactrs are INTERESTING, because they're NOT ENTIRELY OC. Mara found a loophole--OBVIOUSLY, she's MARA--and,she, made HER "OC's" Half-OC-Half-Cannon Characters. She did this by taking the show's CANNON characters, and, adding her OWN spin (putting her OWN creative license into their personalities), into these "cannon characters," by how SHE SAW, and/or, FELT, these characters would act, look, sound, and think in the FUTURE, which turns them from COMPLETELY Cannon, Into Semi-Cannon-Semi-OC Characters. Another example of these kinds of characters, are MY cast of "Next-Gen" OC's, in MY story, "
Genius: The Next Generation (G:TNG)," as I have spent (And Am CURRENTLY Spending) A LOT of time, creating, developing, arranging, and characterizing my OC's, as-well-as, giving MANY THINGS, Thing, Such As,: FLAWS, QUIRKS, WEAKNESSES, [SOMETIMES] Catch-Phrases, REAL, And/or, RELATEABLE Relationships. Seriously, I have to sit-down and think about who's going to do what, what is going to happen, and what, and/or, how my OC's will, and/or, should react BEFORE i write EVERY SINGLE chapter! In fact, I often use MNAY Outlines, and/or, other forms of pre-writing, in-order to properly plan these things out., ...SO, ...ALL I'm saying is, give SOME OC's a chance! I mean, NO ONE has "bad-talked" MY OC's [yet], and I have gotten VERY GOOD, and/or RAVE reviews on how I created, and/or, introduced MY OC's., ...WAIT!,: ...I take that last statement back! SOMEONE (*Stare ANGRILY At That Someone*) HAS "bad-talked" my OC's. That person is NONE OTHER than my good friend Georgia! *Stares Angrily In The Direction, That Believe Australia Is Located In* *Realizes That I Cannot See Australia, And, As Such, Georgia Probably CANNOT fell The Wrath Of My Angry Stare* *Find A Model Globe, And Turn To Australia* *Stares Angrily At It For Some Time* *After I Am Positive That Georgia Can Feel My Stare Burn Through Her Back, I Avert My Stare, Satisfied That She Has Gotten The Message*
...OH, ...And, About The Whole "Orbs, For, Eyes," Thing, I Have This Tow Say,: ...
...I, PERSONALLY, have NO problem with that word. I actually kind of like it, but i can see where you all are coming from. HOWEVER, you all should NOT take Georgia's word for it! She has had a personal, and/or, TRAUMATIC experience with "Orbs." As a child, her parents told her that balls were actually called "orbs," (it was either an Aussie thing, or they were just quirky people), and, as such, Georgia grew-up thinking that balls were called "orbs." when some mean kids at her elementary school began to bombard her with balls, she thought they were hitting her with "orbs," and, as such, she has hated any mention of the word "orbs," ever since. Thus, she is biased.
