Road cyclists are a funny bunch. We have strong opinions about what's cool and what's not. To avoid becoming the victim of a serious bitching session, obey the following protocols:
Take your turn at the front. If you are absolutely wrecked, it is OK to stay near the back where you can draft along, but make sure you inform the captain.
When moving up to take your turn at the front, do so smoothly. Any sudden sprint when moving to the front will be seen as an attack, and will result in serious grumbling among the troops.
At the front, maintain the pace consistently. When the group has two lines, adopt the pace of the rider you followed up the line, and who now rides beside you. When the group is following a single file formation, you may have to use your speedometer to maintain the right pace. You may also need to glance over your shoulder now and then to ensure you have not dropped the group (because you're such a powerful rider of course).
When in formation, do not allow a gap to develop between you and the rider in front. This issue probably irks club cyclists more than any other. While you may be happy to forego the big energy savings available through drafting, the rider sitting on your wheel may not be so inclined. Your drafting of the rider in front also benefits the riders behind. So no gaps please.
If you are struggling to stay on the wheel of the rider in front, wave the rider behind through. This reduces the possibility of gaps developing. Just because you are a wuss does not mean the rider behind should get dropped by the bunch too.
Experienced riders should discreetly point out any mistakes that newer riders are making, and only towards the end of the ride. After all, experienced riders were once novices too. And remember, before critizing another rider, cycle 1 km on their bike. That way, when you criticize, you will be 1 km away, and you'll have their bike.
And a few final thoughts:
Thank courteous drivers with a wave.
Greet other cyclists with a wave too.
If you have an impending shnot or spit or some other similarly disgusting requirement, hold it until it is safe to eject. Preferably when you are at the back of the group, and there are no cars behind. And try not to get it all over your WCCC kit.