Bring the water to a boil in a large, heavy saucepan. Stir the salt in, lower the heat to a simmer. Add the polenta by fistfuls, letting the grain stream through your loosely clenched fingers, and with the other hand, stir as it streams into the water. Keep adding polenta in this way.
Don't stop stirring, and keep the water at a steady simmer.
After all the polenta is in, stir for about 20 minutes. It is done when it comes away from the side of the pot as you stir. You can serve it hot right from the pan, or pour onto a large clean chopping board, work surface, or platter, let it cool, and then slice for further use in whatever recipe you are making.
Some polenta will stick to the bottom of your pan, but don't spend any time trying to clean it. Just let some water soak in the bottom of you pan for about half an hour and it will come off by itself.