My personal rules are simple in the extreme.

1. I am responsible for my own safety.
2. When lane width and other conditions allow for safe lane sharing I ride far right to make it as clear as possible I am sharing the lane and stay alert for potential right hooks.
3. When lane width or other conditions do not allow for safe lane sharing I ride in the outer half of the lane to make it as clear as possible the lane is already occupied.
4. If I feel unsafe on a particular street or road, I do not ride there.

The first three rules are, I think, useful for all riders. The last one can be tough depending on where a rider needs to go.