Justine Larbalestier pontificates on excuses white writers use for not writing non-white characters. As someone whose stories are filled with hispanic surnames and latest novel has Chinese dropping from the skies (not in a "real" sense but in a "that's easy, they're all around us" kind of thing), and I'm not either, that I also struggle with. The best I can do is make them real people. Sure, many are fodder for the sword, but the other people do all the interesting things people do (one Chinese side character speaks perfect English, but when confronted by obnoxious police conveniently forgets they know how, many are shop owners). But it does require knowing "something" about the people you're writing about (name conventions are especially important, not just picking appropriate names but knowing how to put them together, such as the daughter is Kasandra Bonita, not just Kansandra or Kassie).
McSweeney's with their comments written by actual students extracted from workshopped manuscripts at a major university. "Apes, aliens, then dead vampire family = too much Sci-Fi." ha ha ha ha (grokked from Jay Lake, I think)