Upgrading to yosemite? If you aren't a developer then it's a snap. If however you've installed brew this can turn into an arduous task leaving you in limbo for hours. The steps to save you some time are really simple.

Step 1: backup via time machine

I always recommend this prior to any OS upgrade, just for CYA purposes

Step 2: move /usr/local

The yosemite install will hang for hours, mine even stopped. So before you install, just move it like so:

sudo mv /usr/local ~/.local

Step 3: install yosemite

from the app store, duh.

Step 4: move /usr/local back

sudo mv ~/.local /usr/local

happy coding