As Ridge Runner states we all do things differently. My grandfather was a big rancher all his life, and once he told me, 'they know more about being a cow, than I ever will' I have taken that advice with chickens. They know more about being a chicken than we do. I do not bother mine at all. I don't candle them, and I don't expect 100% hatches.
My nests are about 3 feet off the ground, and my hen will pick a nest and stick to it, it is really only big enough for one hen. But I mark my eggs and if she is off the nest, I go take a peak to make sure there are no strays. Often time, while broody is out dust bathing and drinking, other hens will dance in and think - oh this is a good spot. If I have not caught her off the nest for several days, I will carefully remove her. Just to check for extra eggs.
I think a lot of problems people have with broody's is that they try and help, upsetting the hen, which can have her get so upset that they kill the chicks. Seriously day 19, just leave her alone, you can peak into the coop, listen for peeping, say a prayer if you want, but do leave her be.
Now one of the reasons I think Ridgerunner and I have had good success with this, is because we hatch every year. Our flocks are used to chicks. Another reason when you leave her in the flock, she will go out every day or so, stomp around, blow up like a beach ball, chew out the layers, nag at the rooster and stomp around. Everyone learns to give her some space. And we have a great deal of space.
I have tried moving them - yep escaped and went back to where she thought was best. After that, I just hope we get something, and wait.
If this works, you will be spoiled. It is the funnest, cleanest, easiest way of adding chicks. Mama does all the work. 12 weeks in the house? Wow. You will never go back. But it is the longest 21 days ever!
Mrs K