The answer to 'how to clean toilet' is to clean the toilet regularly using a toilet cleaner and a toilet brush. Start by flushing the toilet to wet the inside of the bowl. Apply the toilet cleaner around the inside of the bowl, letting it sit for a few minutes to work. Then use the toilet brush to scrub the inside of the bowl, paying extra attention to the waterline and under the rim. Flush the toilet again to rinse away any remaining cleaner and debris. For the exterior of the toilet, wipe down the tank, lid, and base with a disinfecting cleaner and a clean cloth.
It's recommended to clean the toilet at least once per week as part of your regular bathroom cleaning routine. If you notice any buildup or staining, you may need to clean more frequently. If you're unable to remove stubborn stains or have issues with the toilet not flushing properly, it's best to call a professional plumber for assistance.