Macworld says there are a few things you can do to clean up and prepare your Mac before you take the leap to OS X 10.5 Leopard. Install the latest versions of your current applications (many are rolling out Leopard updates), clean up your hard drive, uninstall unneeded software, run the Apple hardware test and repair your hard drive using Disk Utility. The list of file and folder deletion candidates is especially impressive. First there are the usual culprits like Documents and Applications, but to dig deeper and rid yourself of cruft, look in:
Don't forget you can also use the free DiskInventoryX to ID what's hogging your Mac's hard drive. As for the Leopard upgrade, personally, I plan to do a clean sweep of my Mac and just reinstall my apps entirely. It'll be a good cleanup as well as upgrade, and as a Windows user, the idea of a clean install will make me sleep easier.
- In /Library, /Library/Application Support, ~/Library, and ~/Library/Application Support, look for folder names matching applications you no longer use, and delete them.
- Your /Library and ~/Library folders may contain other folders that store components of third-party utilities. Look in Application Enhancers, Bundles, Contextual Menu Items, InputManagers, and PreferencePanes for any system enhancements you no longer use, and drag them to the Trash.
- Third-party Dashboard widgets live in ~/Library/Widgets. Any widgets you don't use can go.
- Applications use cache files to increase their speed and efficiency, and rebuild them automatically if necessary, so you can delete them safely:
- The contents of /Library/Caches and ~/Library/Caches, can sometimes occupy hundreds of megabytes of valuable disk space. Drag these files to the Trash.
- You can empty Safari's cache by choosing Safari -> Empty Cache (Command-Option-E).
- Safari stores favicons (those tiny icons that appear next to a site's URL in the address bar) separately from its main cache. To remove them, quit Safari and drag the folder ~/Library/Safari/Icons to the Trash.
- Software that requires some component to be running in the background all the time may install folders in /Library/StartupItems. In most cases, you should leave this folder alone, but if you see anything there from software you're sure you don't use, delete it.