I ride in the left of the lane. IMO, it gives me better visibility to on coming traffic as well as they're seeing me. I feel it also gives me more room to maneuver if someone starts to pull in out in front of you from the right. Of course this is just my opinion and preference.
Like Kathy, I ride in the right lane when in groups and that's where the stagger in line allows me to slot in. It's not my preferred place to be. But in groups it is IMO, the safest place to be in the group.
Then when in back road play time, it could be anywhere in the lane that my line is going to require me to be! At that will be all over the lane!!!