In an effort to avoid the dreaded Mary Sue, the Original Character (or Fan Character, whatever you want to call it) application is far stricter than the application for canon characters. Your fan character must have detailed information; you can't just say, 'OH HAY HERE'S MY CHARACTER STACY SHE'S AN UCHIHA LIKE SASUKE BUT SHE HAS A DEMON TRAPPED INSIDE HER LIKE NARUTO!! ALSO SHE'S IN LOVE WITH GAARA KTHX.' Not that relationships between a fan character and a canon character aren't allowed, but if you're planning on doing that then you need to get the other player's permission beforehand. Otherwise you'll just have to settle for a one-sided affair.
Anyway, first off, we'll need some basic information. It's pretty straight-forward. We'll need your character name, age, gender, a brief description of his or her appearance and personality, rank (i.e., genin, chuunin, jounin, anbu, etc.), home country and village, and weapon of choice. Don't feel like your character HAS to be a ninja, either. Ninja are always fun, however you can have just as much fun with any other kind of character too.
Next, going a bit more in-depth, you'll need to describe your character's skills and history. Is he/she more skilled in genjutsu than ninjutsu and taijutsu, or does your character have a basic knowledge of all three? What kinds of special abilities does he/she possess? Explain his/her advanced bloodline, if any (this is entirely optional), followed by a brief description of his or her family history, likes and dislikes (to get a better idea of your character's personality), and personal history. Wrap that baby up with a little bit on his or her dreams/goals for the future (example: Naruto dreams of one day becoming the Hokage, Sasuke wants to avenge his family, etc.). It doesn't have to be something completely serious, and you don't even really need to fill that out if there isn't anything. Then, if there's something that hasn't been covered so far, you're free to add anything else that we ought to know.
Finally, we'll need an example of your writing and how you plan to portray your character, much like the application for canon characters. Have fun, and good luck! :D
Home Country & Village:
Weapon of Choice:
Advanced Bloodline (optional):
A paragraph or two in first person:
A paragraph or two in third person: