I appreciate a well thought out-well developed story line, good character development, and good grammar. I do not expect perfection, but I can see the time and effort put into a story. I prefer the characters to stay in-character. For example, a shy character should not be outgoing in your FanFic, unless you explain why the change in personality took place.
Parodies, if done in good taste, are acceptable.
Humor, romance, adventure, and drama are my areas of expertise.
Exessive vulgar language, or brutality WILL lower your score.
BE CLEAR in your writing. If I am confused about who is saying what, or even what is going on, your score WILL suffer. When more than two people are talking, it is a good idea to list the name of each speaker. That way, not only does it make the conversation easier to follow, it can add more life to a conversation.
Both first person and third person stories are acceptable. Just be sure you know how to effectively use each point of view. If your story is first person, try to limit the reader's knowladge to that of the POV of the character. If the story is thrid-person, you can provide knowladge that none of the characters know. Be creative!