Well, Mary Sues... Mary Sues are like chickenpox: you have a really bad case early on, it gets cured, and it either returns once or twice or it never comes back again. EVERYONE in the writing world has written at least one Mary Sue in their lifetime. They can either get away with it and keep that Mary Sue going, or they can learn how to write well-rounded characters and never make another Mary Sue.
I remember I was making this one character for an original story where Atlantis had risen up from the ocean, becoming the "capital of the world" since half of the continents sank due to it rising up.
The character's name was Kamos, a.k.a "Kamos the Minotaur", so named because he was hard-headed and easy to piss off. He was a skateboarder right on par with Tony Hawk, had a hot mother that liked to touch him, and was highly athletic.
By the time I had gotten to the fourth chapter, Kamos had saved a young woman from her rapist ex-boyfriend (May Bell was her name), boarded a cruise ship with only a handgun, and had stopped and recruited a cute psychic thief from running off with $5,000,000 in Russian bonds (which he kept). Yeah, that has "Gary Stue/Mary Sue" tattooed all over it.
Nowadays, I make sure my characters have several flaws, and are only "perfect" superficially (they may seem perfect, but in the end have a big problem with them). One example is Mitsuki, a beautiful girl that needs the life force of other people in order to survive the cancer she inherited from her father (I think that might... ruin a perfectly good date).
I also have another named Li Yang Fei
Mary Sues are a bit hard to spot, but I have compiled a checklist for any personal future reference:
1. Is beautiful
2. Has a troubled past
3. Gets off easy from any problems she might cause
4. Has mild physical deformities (scar, missing finger or toe) that denote a tragic past but are not detrimental to his/her hotness (heck, they might even add hotness).
5. Is, by comparison, much more "awesome" or stronger than other characters.
6. Looks young, even if he/she isn't young
7. Is a mixed breed of WHATEVER and gets all of the pros and none of the cons of either breed (I am so SICK and TIRED of running across dampers or damphyrs or whatever that are half vampire and they are not scared of the friggin' sun and yet they're half-human and they can't DIE!)
8. Is bi-sexual (Mary Sues tend to seduce almost anyone they run across... they gotta have the motivation!)
9. If a villain seems Mary-Sueish, it must replace the main villain or be the main villain's love attraction, defeat the hero easily, or be more powerful than the main villain. If not, it doesn't qualify as a Mary Sue.
10. Does not have any noteworthy flaws, be they physical, psychological or emotional flaws (economy doesn't really matter. A type of Mary Sue exists called the "CindeSue", a character that is so beautiful and so privileged that it comes through even if it was raised by rats in the sewers).
Anyway, that's all I have to say for now. Anyone ever written a Mary Sue before?