There are several committees, the big one is the Consultative Committee made up of interested parties like County Councils, anti airport groups and airlines. The committee I was on was the the passenger services sub committee. That committee was eventually closed down which was the reason I left but it appears to be up and running again so I was thinking about applying again.
The passenger services sub committee achieved very little to be honest. Most of the members knew nothing about the airport and then there was me who maybe knew too much as I had the run of the place. The committees greatest achievement was to get the passengers rights agreement put up in the terminal. Failures included getting the airports then analogue clocks to all display the same time so the airport had official airport time.
I got on the committee as there was a newspaper article asking people to join. Now I guess you could follow this link
London Luton
Meetings then were formal, with minutes taken so no butting in and were held every 3 months for about 2 hours starting in the afternoons on weekdays.
In my eyes it would be an advantage to know what the issues behind the scenes are and then put over at least one clear point per meeting and that you don't mind attending what looks like a board meeting. Most issues are beyond anything the airport can fix though so it can be frustrating and the obvious issues you might mention will already be known about.