This article was written in reponse to Lion, but it applies to pretty much any OS upgrade, aside from the OS X specific apps mentioned.
- Check you critical apps and anything you just can’t do without for compatibility. (Note: Rosetta is gone! you won’t be able to run PPC Apps)
- Update the Apps that you can.
- Purchase Lion from the App store for $30
- Make a USB stick installer out of because the Lion installer self destructs (kind of) after the install: http://osxdaily.com/2011/08/02/easy-way-to-make-lion-install-disk/
- Backup your files (or better clone your system to an external HD)
- Run Disk Utlities and Repair the Disk then Repair Permissions
- If you’re really careful, run a hardware diagnostic on your machine.
- Run the installer.
- Open the General preferences and check every pane for changes and make adjustments. (for instance you might want to uncheck “Natural Scrolling” in the Trackpad pane if you like the old way to scroll.)
- Write a terse but well argued letter to Apple about the changes your don’t like.
- Enjoy your new OS. And Check out my review of Lion in case you haven’t already. (Which I must update with my Apple app moving trick….)