Thanks to FLX from the SA Forums for this info.
Joining Google+ (as of July 1st)
Receive an invitation e-mail from someone who likes you.
Open the e-mail an click the red “Learn more about Google+” button:
You will most probably be directed to this site:
WAIT FOR SOME TIME AND CHECK THE SITE AGAIN UNTIL IT ASKS YOU FOR YOU PROFILE INFORMATION (it took about an hour in my case until a new page appeared instead of the “over capacity … check back soon” page)
Inviting People to Google+
At the top of your Google+ stream there is a “share” textbox. Enter your message to the lucky invitee and enter his/her e-mail address below:
Click on the e-mail suggestion :downs: and click share:
That’s it. Enjoy waving…uhm, plussing!