Even though your toilet is very dirty, there is no reason to resort to harsh chemicals. Use vinegar and a toilet brush to clean the toughest of toilet stains. Protect yourself with rubber gloves and safety glasses.
Start by soaking the bowl
Add 3 cups of vinegar to the bowl for cleaning. Scrub any stains using the brush. If the toilet is not used regularly, the evaporation of water often leads to a calcium ring at the edge of the water. Allow the vinegar to stand overnight in the bowl with the lid closed to dissolve the build up.
Clean the outside
Fill a spray bottle with vinegar. Spray the outside of the bowl, the tank, seat and lid, and clean with a sponge. Remove the seat to clean the seam where it attaches to the bowl. If the seat and lid are particularly dirty, consider replacing them.
Clean the bowl
Turn off the wall valve and flush the toilet. Spray the inside of the bowl with vinegar and use a brush to clean. For particularly stubborn spots on a white toilet, use a pumice stone to scrub away the stains. Be careful that you don't scratch the porcelain.
Check inside the tank
Lift the lid of the tank to see inside it. If it's dirty, use vinegar and a sponge to clean it. Turn on the valve and allow the toilet to fill.