It depends on what the clicks sound like, faint rapid soft clicks that sound more like a clattering noise, are normal. Do you have a drive acitivity light? The light should be flashing in time with the clicking. Certain brands of drives are louder that others.
Loud sudden single clicks are bad news. They will sound more like someone tapped the top of the drive with a screwdriver. Usually these are accompanied by a momentary lapse or freezing of your PC. These can be just one occasional click, or a steady click.........click..........click..........click for a several seconds.
When you hear this, and you don't usually need to listen closely for these, as they are quite audible, it is a sign you need to save your data immediately somewhere else, and prepare to dig into your wallet.