You boil sweet potatoes by washing the tubers thoroughly, peeling them if desired, and cutting them into uniform bite sized cubes for even cooking. Place the cubed sweet potatoes into a large pot and cover them with cold salted water by at least one inch. Bring the water to a rolling boil over medium high heat, then reduce the heat and simmer gently for fifteen to twenty minutes until fork tender. Drain the cooked sweet potatoes completely in a colander before mashing or serving.