Prepare your Mac for OS X 10.8 Mountain Lion

Apple's next release of OS X "Mountain Lion" is slated for release by the end of this month, with some recent developments suggesting it may be out by asearly as next week. If you are thinking about upgrading your Mac to the new operating system, then you might consider reserving some time this weekend to ensuring your system is capable of and prepared for the upgrade.
While for the most part you should be able to download and install the upgrade without any problems, there are a few things you can do to help prevent running into odd problems.