Hi, i was wondering, when do chicks chirp in eggs (day 21,19 ect), and what to look for when candling?

Chickens may chirp just prior to hatching, day 21. They may not chirp much if at all, but they'll be rolling around as they hatch. Just let them rest and dry off before removing them from the incubator. When candling you're looking for a dark mass in the egg that seems kind of reddish with blood vessels. I'm not great at candling, myself...but that's what you're looking for. Try searching for some pictures online to see exactly what to expect.