Using Google Hangouts On Air to stream a keynote: http://www.conferencesthatwork.com/index.php/presentations/2012/07/using-google-hangouts-on-air-to-stream-a-keynote/
Use a wired connection, not wireless.
Participants should have earphones for listening (audio from the Internet can cause feedback — echo or a shrill noise), video camera on, and microphone on.
Do NOT have any other computers in your room connected into the Hangout.
The moderator can mute participants.
Your YouTube channel must be associated with the same email as your Google+ account.
You can edit the video on YouTube or download it, edit it, and upload the result. Avidemux is free and easy to use.
There is a screen sharing option so you can also present slides or share anything from a Google doc or spreadsheet.
Tell participants to login to Google+ and go their home page and join the Hangout, and where to look for the recording.
If the image jumps too much from one participant to another, the moderator can lock the video on the main participant.