Mac users should a GUI to do the maintenance for us. To run maintenance on you mac get the Tiger versions (10.4) for either Yasu or Onyx. Run all the cleaning processes and let the programs to reboot the Mac. Then do another reboot to rebuild all the startup/shutdown system cache.
Now to uninstall a program with all it's associated files (Application Support files & Preferences) is AppDelete (and it is FREE).
Lastly music & especially video files take up HUGE space! So if you are using a lot of videos consider getting an external firewire (or better) hard drive to keep video files on.
There is also another good review of about 17 tips to effectively performance tune Mac OS X written in the article linked to above. Some of the tips are application tips, others are System Settings, and some are command line performance tuning tips.