The fastest way to boil water is to fill a pot with hot tap water, cover the pot and place it on the stove on the highest heat setting. Pure water boils faster than water with salt or other impurities.
It is important to use an appropriately sized pot to boil water. A pot that is filled to the top boils more slowly because of the depth of the water, so it is best to use a larger pot with less water in it. The pot should have a flat bottom that makes full contact with the burner, and it is important to ensure that the burner is the correct size for the pot.