CH wrote:
how do you know the right frequency mate?
In comps you see the sign on the tail normally first.
In gaggles I try to be in a position, where I do not
see the comp sign under the wings close.

I know not where you are, but here in the US we normally use one of the
two frequencies assigned (more or less) to gliders. In a comp, we
always have a specified safety frequency. For general flying around, we
often have agreements on what frequencies will be used in specific
areas. If I can see the tail markings, I can almost certainly avoid. I
save screaming on the radio for those occasions when I can tell whether
the markings on the wing are mylar or painted...