I recently upgraded to Leopard successfully and I thought I would share my experience and include some guidelines and some troubleshooting tips.

Before I updated my internal drive, I made certain I had two separate clones of my Tiger drive just in case Leopard didn't work well. I have two external drives and I partitioned each drive with three volumes: one for Tiger (80 GB), one for Leopard (80 GB) and the third one for data, including my iTunes music. I cloned my main Tiger drive to both extra drives. I also copied all of my data files from my main drive to one of my external drives.

After I tested the cloned drives to make sure they were working correctly, I set my internal drive as my startup drive in System Preferences and then I shut down my computer. I disconnected all of my peripheral devices except for my display, my ADSL modem, an Apple mouse, and an Apple keyboard. I restarted the computer and inserted the Leopard Install disk.

The Leopard Install disk walks you through the upgrade process but here are some tips that might help you:

1.  After you select the installation type (Upgrade, Archive & Install, Clean Install), click the Customize button on the pane. Click the arrow next to Printers and deselect any printer drivers that you are certain you won't need. This will save you some disk space, especially if you don't need the larger files for Epson, HP, Canon, or Lexmark.

2.  Follow the instructions on the screen to continue with the installation.

3.  After the installation is completed, your Mac will be restarted from the hard drive. Be patient while your computer restarts - it will take longer than a normal restart and it might stay on the solid blue screen for a few minutes.

4.  The Leopard Setup Assistant will open automatically after booting and you can use it to set up your Apple ID and send your registration information to Apple.

5.  After the Setup Assistant finishes, open System Preferences and select Accounts. Click the lock in the lower left corner of the pane and enter your password. If the system won't accept your password, you'll need to reboot into the Leopard install disk. This is, apparently, a bug in Leopard's install program that affects some computers.

When the Leopard install screen appears, select your language. On the next screen, select "Change Password" from the Utilities menu and type in a password for your hard drive (you can use the previous password you had). Next, restart your computer by selecting your hard drive from the Startup option on the Utilities menu. The password problem should be fixed after your computer restarts.

Before connecting to the Internet, turn on the Mac OS X 10.5 firewall. It is now located on the Security pane in System Preferences (it was on the Sharing pane in Tiger).

If there are any new updates to Mac OS X 10.5, install them as soon as possible.