Depends on the situation, traffic before and after the light; if there's heavy traffic after, I'll be able to keep up with traffic and I'll center or left-position myself, if the road is empty afterwards, I'll move to the right tire track to make sure I don't get squished but to allow passing.
If the car coming up behind me is signaling right, I'll move far left to allow them to RTOR. I ride through a light where the majority of traffic turns right, and this being Michigan, hardly anyone ever signals their turn until they're already halfway around the corner, so I assume that EVERYONE is turning right there whether they're signaling or not, and I move far left at that intersection. Almost every day, 4 to 6 cars will go around the corner (without ever having signaled, at least until after they're already into the intersection) to the right while I sit and wait for the light to change.
As I proceed through the intersection, I move back to the center of the lane. I used to hold the left position, but a few months ago I had someone try to pass me on the right. I didn't notice it until I was past the intersection and starting to move back right, heard a noise to my right and realized that I was running the car off the road into the ditch. He eventually got past me and drove back up into the road.
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Work: the 8 hours that separates bike rides.