When riding in a group, especially in a paceline, it's a good idea to point out debris (glass, branches in the road) and potholes so the people behind you whose view might be blocked will be aware of them and won't need to swerve at the last moment or run over them.

I tend to prefer it when people use hand signals rather than calling out every freakin' pebble on the road (inside joke to snapdragen, sorry....), but that assumes I'm paying attention and not off in my happy place