I try to focus on just one of their eyes, and not move my eyes around too much, looking at other parts of their face. I think I've gotten better at it, but I'm not sure how natural it looks to others when I talk to them. I occasionally look away, or it will be too intense. None of this comes naturally and I have to consciously consider what I'm doing. When I talk I usually don't look at people too much, and gesticulate a lot, maybe too much sometimes.
Depends on who I'm talking to and how I'm feeling too of course, sometimes eye contact is difficult and I just want to get the conversation over with.