For these reasons, not installing updates immediately when they are released can be a good habit to get into. It's wise to keep track of new updates as they appear, but try waiting for a day or two to see if any problems are reported on Mac news and information sites such as MacNN, MacDailyNews, Ars Technica's Apple section and Apple's own discussion forums before proceeding with the installation.
When you receive a Software Update notification, you can elect not to install specific updates. In the Software Update pane in System Preferences, you can also disable automatic checking of updates or change the feature to check on a monthly rather than weekly basis. If you disable automatic checking altogether, be sure to run Software Update manually (choose the Software Update command in the Apple menu) on a periodic basis or in response to news that specific updates have been released.
2. Make sure your hard drive is healthy
There was a time (before the release of Mac OS X) when Mac users religiously ran Disk Utility or an alternate hard drive utility at least once a month to verify the integrity of their hard drive directory structures.
A hard drive's directory structures are created when a disk is formatted or partitioned; they're essentially a map of the drive's magnetic platters. They translate the physical sectors that store bits of data on a drive to usable space for files, applications and Mac OS X system components. If they become damaged or corrupted, the Mac can have a tough time locating pieces of files as needed to accomplish tasks like opening files, launching applications and even booting up.
The good news is that technology has come a long way since the days when Disk Utility was a frequent necessity. The default file system for Leopard is Mac OS Extended Journaled, or HFS+J. Journaled file systems keep a transaction log of changes to data on the hard drive. (Microsoft's NTFS is another example.) Should the hard drive experience a problem like an unexpected reboot or removal without being ejected properly -- the two most common causes of damage to directory structures -- the file system can rely on the transaction log to repair the damage.
Even so, hard drives can develop some directory corruption over time, particularly if a hard drive is repeatedly unplugged or removed without being properly ejected or if the drive is formatted using an older nonjournaled file system such as the Mac OS or Mac OS Extended file systems, also known as HFS and HFS+, respectively.