Want to write characters who *aren't* your race, sex, culture, etc? Nisi Shawl, one of the authors of the excellent book _Writing the Other_, gives a short overview of how to do it and not resort to cliches and stereotypes. The overview is one of the chapters in the book.
Well worth reading, again and again. One of my goals is to make characters that are real people, but aren't 40-ish, married, middle class, nerdy, white males (ie, aren't *me*).
Find out more about the book (at SFWA site), and buy the book (at Amazon)!