I put this together (with help) on islandriders.ca and thought someone over here may learn something from it.
GROUP RIDING RULES TO LIVE BY
1. Don't ride beyond your comfort zone
Just because you bought a high performance bike, don't assume that you can make the corner the guy in front of you just carved on his beater. That person may or may not have: years of riding and racing under their belt, carved that corner a million times, rode that bike since childhood.
2. Hold your line
If your going to change lanes ALWAYS signal and then take a good look (shoulder check) BEFORE you change lanes. (lanes = regular lanes and positions within a lane).
a) Passing another rider:
Never pass on a corner as the person in front of you owns the road - GIVE THEM ROOM.
b) Passing a vehicle:
When a group is que'd up to pass a slower vehicle, the rider in lane position 1 (left side of the lane) has the right of way, do not try to pass as this rider might pull out. That said, don't occupy position 1 if you don't intend on passing as soon as it is safe keeping in mind Rule 4.
c) When passing a vehicle DO NOT slow down after you pull out. Instead continue accelerating until a safe distance past the vehicle and then pull in front and over to the right side of the lane so who's ever coming behind you has room to pull in.
4. Don't hold anyone up
If someone is riding close behind you or you suspect even slightly that the person might want to go faster than you, don't go faster, let them pass. Move to the right side of the lane (after you've checked to make sure its clear) and wave them past.
5. Stay away from the front of the pack
Until you have at least a few group rides under your belt its best to stay at, or near, the back of the pack, observe and learn. Riders at the front tend to go faster and ride much closer together. Its not a place to be when all aspects of riding are not second nature.
GROUP RIDING TIPS
Ride in staggered formation. If the group exceeds the speed limit, then go single file, giving the rider ahead plenty of room.
Don't worry about trying to keep up with the group. Someone, or the whole group, will wait for you either down the road, or at the next turn off. Someone will stay at the turn to make sure you know they've turned. In other words don't feel bad or guilty for not keeping up. Group rides are about meeting new friends and and enjoying the sport with other people, fast and slow.
Use arm signals to supplement your bikes turn signals if you feel comfortable doing so.
If you see debris on the road, point at it with your foot if you feel comfortable doing so.
NOTE: Don't assume that other riders in the group will abide by the above rules and tips so do your best to always be aware of your surroundings.