The way I ride depends on the situation...
1) One lane, no bike lane - I ride as far to the right as I feel is safe.
2) Two lanes (or more), no bike lane - I take the right lane, riding down the middle of it or just slightly to the right of center. Basically I'm trying to tell people there is no room for them in my lane, yet trying to maintain a safe distance from cars passing in the left lane.
3) If there is a bike lane, no matter how many car lanes are available, I always use the bike lane.