Can someone explain to me, or point me to an explanation, how to back up my current OS version (10.6.8) before installing 10.10.2 just in case I later have to revert back to 10.6? Is there anything special that needs to be done?
As Artie said, one way is to make a Time Machine backup (you need an external hard drive for this). Then, you can boot from the 10.6 install disk and
follow these instructions.
An alternate method (and you also need an external hard drive for this one) is to clone your existing 10.6 system using either
SuperDuper or
Carbon Copy Cloner. With this method, you start up from the clone and then clone back to your internal drive.
I HIGHLY recommend backing up everything before upgrading to Yosemite (or doing any other software upgrade, for that matter). In fact, it's ESSENTIAL.
