Here is some info on RSVPing for our events.
RSVP 'Yes' if you will go to the event. If you RSVP 'Yes' then *please* attend the event, the organizer is planning on your attendance. If circumstances change and you are unable to attend, please *change* your RSVP to 'No' as soon as possible, preferably in time for the organizer to adjust his planning, but even if it is last second please update your RSVP or contact the organizer by phone if the number is available for the event. In some cases organizers can check RSVPs even from their phones so they will know not to wait for you even if you update last minute.
RSVP 'No' is not required unless you are changing a 'Yes' RSVP to a 'No.' If you do not RSVP 'Yes' it is assumed you will not be attending.
'No Show.' A "No Show" occurs when you RSVP 'Yes' and do not show up and do not change your RSVP to 'No.' Please try to avoid No Shows. It is not the end of the world but is poor form. Meetup tracks "No Shows" to help organizers estimate likely attendance.