First of all, I freely admit that what I say isn't gospel. I am a total amateur at art and writing. I've learned everything that I know via the internet and a few drawing books. It's just that I appreciate all of the tutorials here on dA that have helped me out, and I want to put a little bit of my own methods back in.
Let me get this out of the way: I only write tutorials if I feel that I have something to add to the topic or if I feel like it's one that few people touch on. So then why on Earth am I writing about Mary Sues? Everyone's written about them! And it's true; this topic has been well-explored in countless places that it seems pointless to go over it again. Heck, you can find one of my favorite Sue-torials here (WARNING: THESE THINGS ARE HILARIOUS). I'm not even going to tell you what a