Atleast from my experience, its much easier to notice and pay attention to callous when they ping the area a player may be or an angle that they are holding. Of course you should pay attention to callous but I've definitely been in some situations where everything is happening super fast paced and you may miss a comm that would've been helpful to notice.

It doesn't have to be a specific ping (like danger or watching). You can just ping and say what it means over VC.

This can also really help out new players that may not know the name of every spot on a site.