You can say goodnight to a dirty toilet bowl by sprinkling some borax around the inside surface and into the bowl water itself before you go to bed. In the morning, you'll be able to whisk away the stains easily with a swish of your toilet brush.
White vinegar can also be used as a toilet-bowl cleaner. Pour the vinegar down and around the inside of the bowl and let it sit for 30 minutes or so. In the meantime, use a vinegar-dampened cloth to wipe down the top edge of the bowl and the top and bottom of the seat and lid. Finally, take a toilet brush, sprinkle some baking soda on it, scrub any remaining stains on the inside of the bowl, and flush.