Broody hens used to hatch chicks will require particular attention. Signs of broodiness are that the hen sits tight on her nest and clucks noisily at any disturbance, getting very annoyed if someone should try to get her off her nest. Eggs should be collected regularly if you want to avoid hens going broody, having no eggs to sit on dampens the hen's enthusiasm. If you do want to produce chicks then natural hatching is a far easier, more economical and more interesting way for the small poultry keeper than using an incubator. Chicks hatched between March and June are probably the best proposition.
Make sure that the eggs are fertile and that the broody hen doesn't have too many eggs to sit on, 10 to 12 eggs is a reasonable clutch. If she has too many she will be incapable of incubating them all, and when some have hatched she will abandon the others after a few days in order to take her newly hatched chicks to find food and water. The incubation period for chickens is 21 days. It is advisable to place the broody hen and her newly hatched chicks in a separate coop to avoid the other hens damaging or killing the chicks.