I am on the waiting list. Do I have a chance to join the event?
Answer: normally you do. The organizers will send a message to everyone who signed up either in the RSVP or the waiting list. People who pay for the ticket will normally get a seat. However, to avoid too big a crowd, we sometimes place a cap for maximum number of attendees, and the people who are on the RSVP list has a priority over the people on the waiting list. However, this hasn't happened much in the past.
How do I bring a guest if s/he does not have a meetup account?
Answer: in your meetup RSVP, you can specify how many guests you want to bring. We normally allow bringing of two guests, so just RSVP with +1 and pay for/with him/her when you receive the email.