How do I fix a clicking noise in my bathroom toilet?

Hi Apmollish and welcome to the Plumbing pageat at AskMeHelpDesk.com. You piggybacked on an a 5 year old dead thread so I gave you one of your own. In the future, before you post, look in the upper left hand corner for the date. We need more information.
Tell us more about the clicking noise. Does it happen when you're flushing or when the tank is filling? Does the clicking happen after the tank's filled and the water shut off? What ballcock do you have? (see image).
Back to you. Tom