I've been reading fanfiction for years, and recently decided to write one of my own eventhough its just a short one. Hopefully with time, I will be able to write longer, better fanfic. There are some things that come to my attention when reading all those fanfics. Things that I think I should avoid because it ruins a fanfic. This list will probably keep growing as I learned to be a better writer

1. Everyone is gay / no hetero in sight

This. I find this everywhere.

So the main character is gay? That's fine! That's exactly what slash fanfiction is all about. 

But all his friends are gay too? His brother? Heck, even his parents? Please be realistic here. The odds that all 15 members of Super Junior is gay (and worse, paired with each other) is slim to none. Not even the best author can convince me that it's possible.

And that bit about the parents? I stil remember reading a fanfic where Jaejoong's parents are Heechul and Hangeng, and Yunho's parents are Leeteuk and Kangin. Gee, I wonder how did THAT happen?

2. Character's biography (complete with pictures!)

Writing a good detailed background for your character is good, but please keep it to yourself. I doubt your reader need to know that the main character is exactly 186 cm. Most likely, it won't add anything to your story. And even if there's an important information that the readers DO need to know, try to tell it through the story itself. 

For example:

Name: Kim Jaejoong

Age: 16 y.o

Hair colour: black

Height: 180 cm

Weight: 63 kg

He is an orphan and live with... blah blah blah

Seriously, why would your reader need to know all these trivias? And if the orphan part is important, you can just put it in your story like this:

He turned and sent a smile to the picture sitting on his bedside table, "Goodnight, Mom. Goodnight, Dad."

I'm sure most people understand what the above scene implies. Stating bluntly that he is an orphan even before the story begin just seems plain lazy. And less interesting.

* Some days ago I stumble upon a story with character bio so detailed it should really be called a spoiler

3. Not using the character's name

The tall brunette enveloped the petite blonde in a warm hug. The doe-eyed boy's heart skipped a beat.

Excuse me, who are we talking about?

It might sound more artsy or literary or whatever! And it's good if used in moderation. But doing this too much will only cause confusion. Use their name! That's what names is for. Don't reduce your character to a mere physical description.