Being friendly never hurts. Everyone was new at this sport sometime. Being helpful, but not critical, is even better.
We are tandem riders, and part of my stoker's habit is to wave at all passing cyclists. A friendly 'hi' is not amiss either.
We have ridden the El Tour de Tucson, and many other events, as Bike Patrol, which is a rewarding experience. We get to ride the event and help folks who may be having difficulty; whether it is helping or showing how to fix a puncture, first aid, putting on a dropped chain or words of encouragement.
We've all been there; lets share the joy of riding with others.

Pedal on TWOgether!
Rudy and Kay/Zona tandem