tmux, like other great software, is deceptive. On the one hand, it's fairly easy to get set up and start using right away. On the other hand, it's difficult to take advantage of tmux's adanced features without spending some quality alone time with the manual. But the problem with manuals is that they aren't geared toward beginners. They are geared toward helping seasoned developers and computer enthusiasts quickly obtain the
Make sure that you have the latest version of Xcode installed from the Mac App Store, and that you have the command line tools installed. To install the command line tools, open Xcode, click Xcode->Preferences->Downloads->Command Line Tools
Install brew if needed.
ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"