Broodiness is a natural instinct behavior that is almost impossible to control. When a hen goes broody she will pull out her chest feathers and will sit on the nest all day and all night, rarely getting up to eat and poo.
What breeds do you have? Some are much more prone to broodiness than others. If you are serious about wanting to hatch eggs naturally I would look into getting a few cochins or silkies as they can be very broody birds. A broody hen will hatch any eggs you give her. Broody hens don't care if there are eggs - when the instinct hits they will brood a golf ball or even an empty nest.