I had a hen that started going broody, and to break her quickly, I simply took her off the nest, and put her outside with the others. (You may want to wear heavy gloves as they tend to hate being removed, and will peck you.) I would put a few treats down for them at the same time, so she had incentive to stay out with the others.
I did this every time I saw her in the nest. It only took a couple of days to break the habit. It still took a few days before she began to lay again.
Lower55- If you want to raise chicks, (and you have a rooster), a broody hen can be a good addition.
If you just have hens, and want fresh eggs everyday, then a broody hen is not a good thing. You are paying to feed a non-productive hen. Most will try and break the hen of this habit. Some will put the broody hen in a cage with a wire bottom, (uncomfortable to sit), others put a bag of ice in the nest under the hen, again uncomfortable to sit.