Help with ChatChannels (how to use, etc.)?

So I've reading up on them, but I still got some questions.

A. How does a player get assigned to a channel?

B. When you first enter a game, you get the help message that appears. Does this mean there is already a channel the player already autojoins? Where is this channel defined?

C. Is there a way to auto-assign players to channels w/o them having to type the /join command, at certain points in the game?

D. Does the script itself have a template of a sample ChatChannel I could analyze?

Good luck, here is a tutorial. Tutorial