Keep Your Head Up
While riding in a group, especially at a fast speed, keep your head up and look beyond that rider in front of you. Remember drivers ed, and how they taught you to scan ahead and get the whole picture? The same holds true with us, in that looking ahead to see what's going on 4-5 riders ahead will give you more reaction time in case there is a crash. It will also be helpful in telling you when the speed will increase, or decrease, or if there is something in the road that doesn't get pointed out for some reason.