Another way is to mod the bearing unit so that it sits lower in the moulded housing by sanding down the lip of the housing, or open the bearing housing, remove the spring and cut one coil off it, then replace. Both methods effectively reduce the force that the ballbearing exerts on the shifter casing, which is where the loud 'clicks' come from. Using these methods maintain some of the resistance which helps with haptic feedback when shifting, but help to reduce the noise.
http://www.youtube.com/watch?v=NNJ6O6xnPZQ
This dude mumbles like a motherfucker and seems to live in a dungeon, but if you look carefully he'll show you what's involved.
As I said previously, a blunt chisel is better than a flat-head screwdriver for getting the silver cap off the top.
Have fun!