Creating Story through Character

I usually compose a profile first containing my prototype ideas on a character. From there I design her/him via visual aid. If I'm in an art block, I will compose a MS Paint document containing the character's attributes. Normally I would start my story(ies) before drawing an actual character design. After a chapter is posted, or sometimes after several are posted, I go back and revise my previous chapters. I see if anything about my character needs improving - making sure she/he isn't a Mary Sue/Gary Stu - and see just how well they fit into that fandom (I write fanfictions, haven't written a personal/unique story since high school). If they're too stand out ish, I look for where she/he fell into that category, and fix it. No OC should be a Mary Sue/Gary Stu unless meant to out of entertainment. Now, even though I have been writing a lot, and do try to keep my OCs as real or as true to the fandom, mistakes do happen. However, when a mistake is made, and pointed out, I correct it as best I can.