I have learned to not trust anything out there, including the road itself, or my own bike. My two primary things to avoid are other vehicles, and fixed objects like light posts, potholes, curbside post boxes, and curbs. I think my over-arcing theme & rule is to never go anywhere that you can get boxed in with no way out. This includes staying well clear of wide vehicles, not going too far right on streets lined with parked cars, waiting for lulls in traffic to do any move that would otherwise be risky, and trying to keep my tires dry and clean. In my "cyclists mind" you cannot assume anyone will see you ever, assume instead you cannot be seen, and assume they will act erratic & not follow traffic law. So in short, i only ever claim a spot in a lane if it is required for safety (avoiding something etc), everything else is secondary.

- Andy