1) There is nothing magic or sacred about avoiding the center track of your lane. Debris usually ends up not in the center track, but on the lines on a freeway. Since there is so little stopping on a freeway, the center track is usually not significantly more greasy than to either side of it. So, in high wind situations, favor the center track. Passing between a pair of 18-wheelers, use the center track. Riding in the fast lane with a guard rail or retaining wall near by, use the center track.
2) Assuming you are in the slow or second slowest lane and you approach an on-ramp, do a head check to the right. Equally as important, if you are approaching an off-ramp, do a head check to the LEFT (and catch that guy who is about to cut in front of you to make his exit).
3) If it's shiny or black, ride a different track. Just because you are in staggered formation does NOT mean that you have to stay in your track. There is a whole lane at your disposal without encroaching on the traffic rights of other motorists. You ride staggered to give you maneuvering room in case you need it. Rather than ride over a patch of shiny or unusually black surface, assume you need it.
4) Do not assume your mirrors only say NO. That is, if you see a problem in your mirrors, they are telling you NOT to move into that problem. If they do not show you a problem that is not the same as them saying YES, make your move. Head checks every time are for your safety.
5) When riding in a group it is far more important to put your most qualified/experienced/prepared rider in the drag position than it is to put that person in the lead. This person is, after all, the first person who will need to deal with an accident, is in the best position to observe the riding skills of the others and recommend changes to accommodate them if need be, and is the person that most often obtains that new lane for the group. That's plenty of activity and responsibility, and merits the best, not the worst of the group.
6) Remember, arriving at your destination safely is the most important part of any ride.