Writing is not what non-writers think it is :)
Some fiction writers will often take a relatively small incident from their lives and weave a whole story behind it. I know I do that. Thus, the thinking: you write what you know. But even that isn't always the case. You know the event you're weaving the story around very well because it happened to you; you lived it. However, that event can be too small to build a 300 page story upon, so your imagination kicks in.
This is where the "you think you know what you're writing about" comes in. This is where you find out that there is lots of research to be done. It is entirely possible to spend hours on the internet reading other people's research. You could conceivably write a story based solely on that kind of research, but I think writing a story that way gives the story a somewhat sterile feel. So what do you do then?
You talk to people; experts. In my case -- because I've been blessed with having lived a full life and having met people in all, and I mean all walks of life -- it means I harass those friends for detailed information. I don't know how they put up with me! Sometimes I can't put up with myself!
You might also physically visit sites that give you a feel for the places that will serve as background for your story; places you believe will give your story the right feel.
All of the above takes time. I am often asked "When's the next book coming out?" Divergent Lives is slated for release December 12, 2012. I am 160 pages in and the deeper I get into this story, the more questions I have for my expert friends. So, for this story, I'm working hard to meet a deadline I set for myself and trying not to overstay my welcome in my friends' brains; trying really hard not to get on their nerves!
Because I always try to come from a place of gratitude, I believe this is a good time to publicly thank those friends, particularly: J. Salgado-Reyes (who also doubles as my publisher), D. D'Avanzo, P. Bazin and B. Benjamin. These fine gents have been extremely patient with me having spent countless hours on the phone with me and exchanging emails in which they answered question after question about the minute-est detail I can come up with. Sometimes they did this at ungodly hours! Thank you!!
The people named above, along with many others, keep me excited on a daily basis! They keep me inspired! Buoyed! Even though this story was borne from a very small - tiny - incident in my life, the idea is engorged by my imagination. I live each and every one of my characters' emotions and I adopt their way of thinking as I write the story. It's hard to live out a character's life in a year's time when you haven't even lived out your own life. It's hard to capture in writing how a character might or might not react to a situation -- with or without justification for that action. But I will never stop doing this.
The plus is, that unlike your own life, you know the ending to the story you are writing.