Kappy's Personal Suggestions for OS X Maintenance
For disk repairs use Disk Utility. For situations DU cannot handle the best third-party utilities are: Disk Warrior; DW only fixes problems with the disk directory, but most disk problems are caused by directory corruption; Disk Warrior 4.x is now Intel Mac compatible. TechTool Pro provides additional repair options including file repair and recovery, system diagnostics, and disk defragmentation. TechTool Pro 4.5.1 or higher are Intel Mac compatible; Drive Genius is similar to TechTool Pro in terms of the various repair services provided. Versions 1.5.1 or later are Intel Mac compatible.
OS X performs certain maintenance functions that are scheduled to occur on a daily, weekly, or monthly period. The maintenance scripts run in the early AM only if the computer is turned on 24/7 (no sleep.) If this isn't the case, then an excellent solution is to download and install a shareware utility such as Macaroni, JAW PseudoAnacron, or Anacron that will automate the maintenance activity regardless of whether the computer is turned off or asleep. Dependence upon third-party utilities to run the periodic maintenance scripts had been significantly reduced in Tiger and Leopard. These utilities have limited or no functionality with Snow Leopard and should not be installed.
OS X automatically defragments files less than 20 MBs in size, so unless you have a disk full of very large files there's little need for defragmenting the hard drive. As for virus protection there are few if any such animals affecting OS X. You can protect the computer easily using the freeware Open Source virus protection software ClamXAV. Personally I would avoid most commercial anti-virus software because of their potential for causing problems.
I would also recommend downloading the shareware utility TinkerTool System that you can use for periodic maintenance such as removing old logfiles and archives, clearing caches, etc. Other utilities are also available such as Onyx, Leopard Cache Cleaner, CockTail, and Xupport, for example.
For emergency repairs install the freeware utility Applejack. If you cannot start up in OS X, you may be able to start in single-user mode from which you can run Applejack to do a whole set of repair and maintenance routines from the commandline. Note that AppleJack 1.5 is required for Leopard. AppleJack 1.6 is compatible with Snow Leopard.
When you install any new system software or updates be sure to repair the hard drive and permissions beforehand. I also recommend booting into safe mode before doing system software updates.
Get an external Firewire drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):
Visit The XLab FAQs and read the FAQs on maintenance, optimization, virus protection, and backup and restore.
Additional suggestions will be found in Mac Maintenance Quick Assist.
What is the best software program to buy to clean up my mac?
Leave your Mac on one night a month, (not in Sleep mode) so it can run maintenance tasks for you.
Read here > Mac OS X: About background maintenance tasks
If the drive is slow to respond to tasks, you may need to free up disk space.
Read here > Freeing Up Hard Disk Space - Mac Guides
DO NOT use Onyx or any other app, it is 100% unnessary. Your machine will do daily, weekly and monthly maintenance routines if allowed to do so. If you want to see when these were last run or manually run them you can download and install http://www.giantmike.com/widgets/Maintidget.html. If you leave your machine on 24/7 and only let the monitor sleep these routines will run in the middle of the night. This is the best method for having a stable machine.
I am guessing you may have recently switched from a PC were you may have been used to performing maintenance on your computer in order to try and keep it in good shape. On a Mac there really is no maitenance to do, simply read your owners manual carefully and it will provide the instructions you need. Here is a useful article to read:
Hi, if you're not confused yet, I think you should get Applejack...
After installing, reboot holding down CMD+s, (+s), then when the DOS like prompt shows, type in...
Then let it do all 6 of it's things.
At least it'll eliminate some questions if it doesn't fix it.
The 6 things it does are...
Correct any Disk problems.
Clear out Cache Files.
Repair/check several plist files.
Dump the VM files for a fresh start.
Trash old Log files.
First reboot will be slower, sometimes 2 or 3 restarts will be required for full benefit... my guess is files relying upon other files relying upon other files! :-)
Disconnect the USB cable from any Uninterruptible Power Supply so the system doesn't shut down in the middle of the process.
AppleJack is very useful, especially for people who don't have an external drive to boot from, or at least a second bootable partition. But there isn't yet a version compatible with Lion (and if the past is any guide, it will be months before a Lion-compatible version is released - or never) and most computers with Lion installed have the Recovery HD partition from which they can boot.