Check that the toilet is properly installed. Ensure the base of the toilet is solidly attached to the floor.
Try to move the toilet. If it slides, rocks or twists, it is not properly installed. Check for any leaks. Your toilet should be completely leak-free.
Clean the toilet on a regular basis to prevent degradation from bacteria buildup. Avoid using drop-in cleaners in the tank, because they can damage the rubber flapper and cause leaks. Discard a cleaning brush after it has worn down, because the metal beneath the bristles can damage your bowl.
Maintain a constant water line in the tank at all times. If you notice your toilet flush getting weaker, adjust the water supply line slightly to let more water into the tank.
Check the seals on the flush ball periodically. If your toilet flushes on its own sometimes or runs when not used, you may need to replace the flush ball.
Cut down the water supply slightly if the tank is loud when refilling. Reducing the water pressure should stop the noise.