I'd really encourage Mac users to install OnyX. This maintenance program is completely free and will help you keep your Mac clean and in perfect running order.
The first time you run OnyX it'll verify S.M.A.R.T status of your disk to prevent failure and analyze the structure of your volume. Every action is well explained and OnyX even features a thorough help guide.
OnyX will let you set a number of parameters all over your Mac including Dock, Exposé, iTunes and Spotlight. It is most effective at fully cleaning your files including system, user and fonts. You'll have to make sure all other applications are closed to allow it to function properly though. The automation section in OnyX will let you maintain, rebuild and clean your drive.
Obviously, some of these operations will take some time to perform, however you should see some notable improvements in the way your Mac runs afterwards.
OnyX is a very handy application to have around. It'll ensure your Mac is always clean and tidy. And best of all, it's completely free!
