All I want to do is. . .

. . .install Homebrew.

Description: Homebrew's tagline is "the missing package manager for OS X". It is by far the best package manager for Mac available and will save you hours of yak-shaving.

Updated: 02/09/14

Works on all MacOSX >= 10.5.

Updated 2013-09-15: Add instructions for inserting into PATH.
Updated 2014-02-09: Update install command.

# In your Mac Terminal, run:
$ ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"

Then, make sure /usr/local/bin is at the top your PATH environment variable.

# In your ~/.bashrc, ~/.bash_profile, or ~/.zshrc (for zsh users)
# ...
export PATH=/usr/local/bin:$PATH

Run brew doctor and try to fix as many of the listed issues as possible.

$ brew doctor

Thats it!