Just remember to invite your NG circle when you start a hangout. I have a list of NG Google+ users that I have shared on Google+ and you can simply choose to add my NG circle to your circles. If you are not in my NG circle, send me a message on Google+ and let me know you are a NG fan.
When the person who starts a hangout leaves, the hangout will show up as being over on Google+, even if people are still in there. If you join a hangout it doesn't hurt to invite your NG circle. That way as long as you are in there people can join the hangout from Google+. If a hangout is full, feel free to start another one.
You can check your Google+ stream to see if your hangout, or someone else's hangout, is showing up with the option to join it. If it isn't, INVITE.