Many people don’t realize but the Mac OS is self-healing, and will fix many of the problems you encounter automatically. The catch is, these functions are run via scripts that are scheduled inside the OS to execute in the very early morning hours, when most people are asleep. But, No Worries, you leave your desktop computer on all the time any, right? But does it go to sleep? If it does, then this maintenance will not get run. If you have a laptop, do you leave it open and plugged in, making sure it is not set to automatically go to sleep? Again, in sleep mode, these won’t get run.
Now, there are three separate scripts that get run, Monthly, Weekly and Daily. All three run at their respective times on the calendar. And just to negate what I previously said, the Daily scripts will run the next the machine is activated, and occassional the Weekly will too, if it missed its previously schedule execution. But the Montly scripts do not run automatically if missed.
The Monthly script does most of the major maintenance on the machine, ie Optimization (or Defragmenting for you Windows folks). So ironically, if you leave your machine running overnight for a few consecutive days, your machine quite possibly will begin to run a bit better. The scripts allow the machine to look at itself and move files into an orderly fashion so it knows how to find them more efficiently, saving you the time and headache of having to wait for it to do something. It will also perform checks on itself and do what it can to correct any problems that do not cause drastic changes to your system.
Now if you are like me with an Apple laptop, it is not always easy to remember to leave your computer up and running all night for a few nights. So there has been software developed that will allow you to force these utilities to run and clean up your machine. Titanium Software, a French group, has designed some of the best utilities I have found, and the best part… they are Freeware. They have released 3 separate utilities I use, Onyx is an all-in-wonder package giving you the functions to repair, modify system properties not available directly via OS X, and other cool and fun stuff. The second 2 are Maintenance and Deeper. Maintenance is just what it says, the maintenance tools from Onyx. So if that is all you want, then that is all you need. If you want access to just the customizations that Onyx offers, then Deeper is tool for you.
These are great tools and will likely give you better control of your system. You will need to be an adminstrator on the machine in order to run Onyx or Maintenance. So start giving your Mac a helping hand and not abusing it so much. Take care of it, and I promise it will take care of you. 
