Lucky thing. We had one sitting a month or so ago but a helpful neightbour decided to shove in a load of extra hay and it meant the eggs got buried and crushed. Grrr....
Anyway what do you want to know. I'm still getting to grips myself but this is what we found...
When they hatched last year we had a problem with rats. They didn't take the chicks but burrowed into the run leaving gaps where the chicks got out to be met by cats, magpies etc. So make sure you keep them safe until they are big enough. We moved ours to a seperate pen for safety this year.
She won't necessarily sit on them ALL the time (although pretty much) - even if they go a bit cold they still seem to hatch which surprised me. She is meant to come out one a day to feed, drink and poo. So make sure your feeding co-incided with this. Our "helpful" neighbour also used to let her out at the crack of dawn before I got chance to feed her and then she wouldn't come out again.
Ours seem to stop the other chickens from laying when sitting which was a bummer. Ended up with no new eggs all last summer which was why we seperated her this year.
Finally you are meant to feed the chicks on something called chick crumb but we used to just crush up the corn a bit and it worked just as well. Make sure they can't drown themselves in the water too.
Good luck. Remember they might not all hatch and you will probably loose a few even if they do. After a couple of days she will leave any eggs she thinks are duff to care for the hatched chicks. Enjoy. They are Sooooooooo cute