How do you decide on which males to keep?

[Sasha-chickens]

I haven't had to do this in a while, but since I've restarted my flock, I now have 19 hens and 18 roos, all the same age. (How was that for a split? LOL) I only want to keep 4 of the males. They are currently 5 weeks old, starting to crow and become obnoxious, and separated from the (mellow) hens. How would you all go about choosing the 4 lucky ones?

If there is any aggressive males I would remove them. Maybe if you have some that are annoying (LOL) I would remove them.