Lifestyle photography can mean many different things depending on who you talk to. For me, I try to keep things really, really simple. Lifestyle photography for me behind the camera is all about life.
Sometimes this means capturing life as it happens without staging the shot at all, while other times I'm setting up the "perfect" shot, checking lights, poses, etc, etc. Just because the shot may be somewhat staged doesn't mean it couldn't have happened naturally, right?