Author has written 1 story for Harry Potter, and Shakugan no Shana.
25 year old American male writing as a hobby.
The thing I value most is intelligence. My definition of intelligence is knowing your own limits and the limits of other people, and differentiating between knowledge and wisdom as well as ignorance and stupidity.
I believe stories are about expressing something. It might not be clear what is being expressed, even to the author, but something will always work its way through. The best stories are the ones where the author is intimately familiar with what they want to express. Writing skills can be honed over time, but there's an innate talent for expressing yourself that makes for the best authors.
Pet Peeves in Writing
1) Terrible teaser summaries. Don't ask questions in a teaser- ie, 'what if X.' Just tell us what your story is about. Including a quote from the fic itself into the teaser- I hate that too. Including any kind of line that isn't about the story is also bad. HxG or NaruHina or whatever is fine, but don't put 'don't like don't read!' or some other non-story related phrase in there, because to me that says 'I have no confidence at all in what I'm writing.'
2) Pretentious writing. Using excessively sophisticated vocabulary. It probably pisses me off because I have a tendency to do it, and it's annoying. The narration should include normal speech (as in, what people in the world actually say, not artificially perfect scripts) and not robotic sounding text.
3) Character bashing. It's admittedly a really subjective peeve. A character with the 'good guys' can be a complete monster without being bashed if there's a reasonable chain of events leading up to it. Conversely, not acknowledging characters' flaws or writing them out is equally annoying. The golden rule I would use here is, if I can feel the author's voice behind the words, it's invoking this peeve. If I can guess the author's opinion on all the characters from reading your story, he or she has failed as a fan-fiction author.
4) Naked dialogue, or via TVTropes: the Featureless Plane of Disembodied Dialogue. I hate having to re-read a section of dialogue three times just to figure out who is actually speaking. It makes it hard to actually picture the conversation.
5) Fics where it becomes very obvious early on that nothing is ever going to challenge the protagonist, and that the entire fic is going to consist of the MC fixing everyone's problems and administering beatdowns on the villains.
6) I like italics. Everybody likes italics. It's a great tool to emphasize words. The problem is when you keep using them every other paragraph. If you're finding that you really want to emphasize a certain word but you've already been using italics nearby in the narration- reread the sentence again, ask yourself if it really needs emphasizing. If it does, you can find some other way to do it. It's an eyesore, and every time you use the italics you decrease their power for when they're really needed.
7) The phrase 'precious people' which I can only assume is a translation of 'nakama' from Japanese because the translator thought that 'friends' wasn't a strong enough word. Listen to me- nobody says the phrase 'precious people' in real life. It sounds awkward and dumb. I cringe every time I read it. You know what works just as well 99% of the time? Whenever you feel yourself tempted to write the phrase 'precious people' replace it with 'friends' and then reread your sentence. I guarantee you it will sound better.
8) Super!Harry/Naruto/Ichigo/Etc fics. This is especially bad in Naruto, where I swear you have to wade through pages and pages of 'Replace the main character with somebody smarter' to find a fic with an original premise. I don't have anything against this type of fic on principle- there are quite a lot of good ones, it's just been done to death already in all of the biggest fandoms.
9) Author Tracts- when the author speaks through the characters, often in a very obvious manner, about something they care about a lot in real life. I don't care about your pet issue, not while I'm reading for fun. I can agree with you 100% with whatever it is you're preaching about, but the fact is if I wanted to be preached to I'd go to church. It takes me out of the narrative.
10) Replying directly to reviewers in the chapter. If you're speaking to all readers in general in an A/N, that's one thing, but going through every individual reviewer and replying to them is just silly. There is a Private Messaging system for exactly this purpose- when you want to reply to someone specifically, you should do so through PM. It's just annoying and looks unprofessional and gives me a very bad impression of the author which colors my perception of the story.
Things I Like in Stories
1) I like a viewpoint character with an abnormal mental state. Paranoia, schizophrenia, a made-up mental state, extreme aggression or viciousness, whatever. I prefer more fictional variants; real life insanity would just be awkward and strange and probably not actually very interesting to read about, but I like stories where the main character isn't 'all there.'
2) Using magical/mystical/sci-fi means to enhance character interactions. For example, a character can read another characters mind, or a character is forced to speak nothing but truth; the kind of thing that is impossible in real life but can be quite interesting in fiction. It's hard to invoke this kind of thing in a new and interesting way as it is done quite a lot but there are fortunately a lot of ways you can go with this.
3) SIs are my guilty pleasure.
4) When the author has the character voices nailed. It's a pleasure to read stories where all the different characters sound as if they could've come straight from the source material. You'd think this would be a given but I find it astonishingly rare. It's a talent to be able to write a diverse cast of characters without them coming off sounding similar.