Are you in the south? We live in southern KY and it's getting late in the year here for hens to be hatching new chicks. It takes 21 days of setting and then several weeks for the chicks to feather out well enough to tolerate the cold without mother covering them and keeping them warm.
I just had a cockoo maran go broody and she hatched 10 chicks a week ago. It was her second hatch this summer. I also had a barred rock hatch chicks this summer as well. So, 3 batches of chicks total this summer. I use the same methods already described here to encourage the hens to go broody. I use 6 fake eggs per nest and the nests are relatively dark with a cover over the top and the entrance facing away towards the darker side of the coop.
Hope this helps,
Guppy