While most of us Mac users will have a pain-free, ‘easy does it’ half-hour upgrade to Leopard this weekend, others may be surprised at what’s broken or causing a conflict with the new cat in their Mac. As I began my own in-house clean up, I thought I might pass along a few tips for others who will be an early adopter of Leopard.

1.) Backup!

It can never be said enough, or practiced enough- there is never a backup that’ll you do that you’ll curse, save for the times when you overwrite an existing backup you later realize you need. When leopard hits and Apple’s own built-in, dead-simple approach to backing up your files with Time Machine lands on Mac desktops & hard drives everywhere, perhaps this message will become less important.

But before you upgrade, it’s the single most important step. With a full bootable backup, you can botch your upgrade beyond any tawdry 1.1.1 iPhone bricking ever done, and still in a moment’s grace boot from your backup and recover. Consider CarbonCopyCloner (already Leopard ready) from Bombich Software to make your bootable clone.

2.) Sour Milk Apps

There’s nothing like incompatible, out-of-date software that ‘sort-of’ runs on a new OS to give you an upgrade headache. To ensure that you’re running the latest and greatest for all the applications on your system, try the free ‘Application Update‘ widget by Georg C. Kaindl.

The widget can be configured to check the versions of your existing applications against those listed on MacUpdate and Version Tracker and provides links to download the latest versions of them.

If you’re even more astutue, check wit the application’s author to find out whether the application(s) you have are Leopard-ready or not.

3.) What’s Starting Up Might Slow You Down

Check your startup items (System Preferences-> User Accounts-> Login Items tab) for any items that might not play nice with Leopard. For example, I have Quicksilver, StickyWindows, and Smart Scroll X all set to start when I boot or Log In to Tiger. For the upgrade, I will remove these items from the list, and have Apple-only items in the list remaining.

Secondly, I’ll check with the software’s authors for any updates known to be compatible with Leopard, and install them if available after upgrading. If not, I’ll wait until they are before attempting to use them. Most developers have prepared at least betas which work with Leopard, while others can be expected to have Leopard ready versions of their software within a month or so. That said, the vast majority of programs will work out-of-the-box with Leopard.

4.) Virginize Tiger

While iPhone unlockers clamor to have a ‘re-virginizer’ to clean up their hacked phones for the 1.1.1 update, so to should Tiger users with OS mods get them out if possible. Software like Unsanity’s Application Enhancer, Interacto’s UNO gui changer, and other application specific modifications like Kent Sutherland’s Chax for iChat should be uninstalled for good measure.

As with before, check with the authors of your modification software for Leopard compatibility. Likely if you don’t install these mods you won’t be able to uninstall them properly after the upgrade, and they won’t work either.

5.) Time Machine Should Be All Alone

Post-install, let’s assume you’re up and running and everything ‘appears’ to be going smoothly. You’re cruising through Coverflow in the Finder; wasting precious working time moving application windows near the dock to see the reflection effect; building Stacks and Spaces, and cycling through the new desktop backgrounds. All may seem okay, but that’s no reason to destroy that backup of your previous system. If you setup Time Machine, do it on a fresh partition on an external drive separate from your pre-upgrade backup.

Should anything go awry and you need to recover files, applications or settings that you had from before you switched cats, you’ll be glad you kept that backup. After a few months down the road when you’re racing along with Leopard, feel free to delete that old dusty backup if you need the space.

Hopefully the above tips help those who’ll be upgrading soon. If there are any other tips you readers think of to help with the transistion, feel free to post them in the comments.

Happy upgrades, all.