here, we have always used the "headache" statement when tossing/dropping little stuff.
I like the idea JPS had of double calling or command/response. I sometimes use that when im on the ground and a climber yells out.
We too tell rookies that if they hear a saw running, look to see what is being cut BEFORE they enter the work zone. if a chipper is obstructing hearing ability, look anyway, as they may not get the 'clear out' signal.
One guy here tell his hands that and if they get hit, its their own dam fault. that one warning is all theyre going to get. I know this is not smart, but i do like it to a sense as i get tired of always yelling 'headache'. Its kind of like, 'catch a clue man, im cutting up here so stay out of the way. look before you cross.' you know, you would cross a street w/o looking, same here applies.
I also feel it is the responsiblity of groundies to communicate w/ each other. Ive had fellow groundies walk under the climber w/o a care in the world while cutting was going on. No one has been hurt, but i take it as my responsibility to keep my fellow groundies safe.