Responsive Tweaks

I generally like being aware of common criticisms in fiction and trying to make sure I don't fall victim to the same thing. We can naturally get into schools of thought based on the media we consume on a regular basis rather than the world we live in. So, I plan to make these changes to my trilogy:

More ethnically representative - It kind of hurts that I didn't think of this earlier (or at least until I got to Book 2, which has much more depth with a black character, an Italian character, and a working class neighborhood).  As someone who is older and more experienced now, this is going to be one of the massive changes I instill on this editing round. I have the perfect platform to do it in, as my characters should all naturally be from places around the world. Some of the main characters have specific ties to America and I'm keeping those in (country of origin, after all), and I am going to try to make sure the "bad" characters are not of any ethnic origin, to eliminate stereotypes. I have already made two of the more prominent characters British (well, one is of unknown origin, but was raised by the other British person), which I believe adds to the "slightly foreign" effect they have on the main character. I can't wait to start exploring minorities as I progress, though.

More humanized "villains" -  This is mostly for the second book, where I have to make sure the nasty people they meet are still sympathetic and not just Generic Evil, especially since some of them are children. It's going to be quite a while before I get to seriously editing those scenes, but I really don't want to equate working class with nasty.

Okay, now I just have to figure out what a Mary Sue is and why it's so bad. (Can anyone help?)