After laying a clutch of eggs in the nest (8 to 12), a goose will sometimes get the natural instinct to go 'broody' or sit on her eggs. Medium weight geese seem to be the better broodies and some heavy breeds like the African and Toulouse will break their eggs.
She may not always sit on her eggs, often with the way that breeds have been modified through selective breeding, this characteristic is lost especially if the breed has been created as a utility bird for producing meat or eggs. If she does go broody and decide to sit on her eggs, she might line the nest with a few of her down feathers and then when she decides to start sitting on her eggs, she will not leave the nest except for short periods of time for food and water.
Always ensure there is sufficient nesting material available for the goose to nest with and a thick enough layer of shavings on the floor as the goose may like to make a hollow to make her nest and if she hits a solid surface, her eggs may get damaged.
If the nest is outside, ensure the goose is protected from magpies and crows (laying cut branches around open entrances can help).
Be careful if you go near her as she will be very protective over her nest and you may get pecked if you go too close, more likely by the gander as he has nothing to do except guard his goose at this time! Later on during the incubation period, she will probably leave the nest a little more for slightly longer periods of time.