Using tmux for collaboration

Summary
An old coworker of mine recently showed me the wonders of using tmux when pairing up. Using tmux you can easily share your screen with multiple people and both observe and make changes. Rather than pull a coworker from across the call or use a join.me session you can easily show them something with just a couple of quick commands.
Setup
Copy the below to your .bash_profile and then source that file (source ~/.bash_profile).
Usage
Creating
To start a session that someone can join, simply type tmux-start and a session name.
The way tmux works is it drops a pid file in /tmp with your session name. Normally this pid is readable by the user that created it. The chmod 777 changes the file permissions to allow this to be readable by all.
Listing
You can list the current sessions by typing tmux-list. This will spit out a list of the users and the name of the session for which you can join.
Joining
You can join a session by typing tmux-join and the session name.