Update brew and formulas
$ brew update
List installed packages
$ brew list
Install packages
$ brew install ansible
Find old installed packages
$ brew outdated
Upgrade everything
$ brew upgrade
Upgrade one formula
$ brew upgrade ansible
Stop something from being updated
$ brew pin $FORMULA
Reverse:
$ brew unpin $FORMULA
Remove old versions of package
$ brew cleanup $FORMULA
Remove all old version
$ brew cleanup
View what needs to be cleaned
$ brew cleanup -n
Edit a formula
$ brew edit ansible
Problems after Yosemite upgrade? answer