The Mountain Lion installer doesn’t ask you to pick an installation method, as was the case for early big cats. However, you still have some choices. You can approach the process in any of three ways:
•Plan A: In-place Upgrade: This easy, default method is appropriate for most people, with some qualifications.
•Plan B: Clean Install: Although the installer no longer offers an option that lets you start fresh by erasing your disk, you can accomplish the same thing in a slightly roundabout way.
•Plan C: Install over Leopard: Leopard users who can’t—or don’t want to—first upgrade to Snow Leopard have their own path to follow. (Tiger users have to be even more creative; I address the needs of those few people in the ...