Staying Safe on Group Rides

Probably the most important rule of group riding is good communication. Ideally, the leader will explain the ride in advance pointing out any safety considerations such as rough roads, high-traffic areas, easily missed turns, etc.  Below are a few guidelines for riding in groups and staying safe. 

Speak Up
If no one seems in charge, you should speak up and ask, because sometimes there is no formal leader and the assumption is made that everyone knows what's going on simply because they've come out for the ride. This is sure to cause problems. If you don't know, ask, and keep asking until you find someone who can tell you what's going on. There are always a few people who know and are willing to help and it can make a big difference in how much you enjoy the ride and how safe it is.
There are a few more situations that would require you speaking up during a group ride.  One is road hazards such as potholes.  If you see a pothole, or hazard of some sort in the road ahead, make sure you call it out so those behind you know it's coming and can avoid it.  There's nothing worse than unexpectedly running into a pothole and flatting a tire or denting a rim.
Another situation that requires some communication is rearward approaching traffic.  If there's a car coming up behind you and there are riders ahead that aren't quite far enough to the right of the lane, yell "car back".  At this time the riders ahead should move to the right of the lane allowing the car to pass more easily.
Lastly, if you suddenly have some sort of mechanical problem let everyone know that you're having a problem before you come to a stop.  Instead, of encountering you problem and slamming on the brakes, simply slowly roll to a stop. 

Use Signals
It's always a good idea to signal your intent.  Signal with hand gestures for stopping and turning or moving into a paceline.  You never know how tired the person is behind you is, so you always want to signal in case they're dazed and not paying attention.

Pay Attention
Once the ride is underway, you can learn a lot about a group by watching the other riders. Try to find and avoid those who wobble and speed up and slow down. These are signs of poor handling skills and possible fatigue that can cause a wreck. Instead, try to ride with the people who hold a steady pace and a straight line because they're less likely to do unpredictable things that can cause mishaps.

Don't Overlap Wheels
When cycling in a group, always pay attention to where your front wheel is in relation to the person in front's rear wheel. Keep your front wheel behind his rear wheel, not overlapping it. Why? Because, if he suddenly veers to avoid a hole or rock, his rear wheel will knock your front, which will send you flying.

Use Care When Looking Back
Another extremely dangerous maneuver is turning around to look back like you might do if a friend was on the ride and you were trying to figure out where she was. There's one safe way to look back (for an experienced rider) and it requires a willing helper. To do it, ask the person next to you if you can rest your hand on their shoulder while you look back. They'll say yes and you can then hold on and look back. Having your hand on a shoulder prevents you from swerving as you look back and it keeps your bike going at the same speed as the other bikes preventing slowing that could cause problems. Practice this tactic with a single riding partner before trying it in a group.

Proper Etiquette
There's always the challenge of expectorating in the peloton (a bike racing term for what the group is called). Everyone has to do it, so don't hold off. But, do it carefully so you don't soak your ride partners and get banned from the next ride. Always spit with the wind and away from riders. If this means steering to one side of the road first, go for it (but only when you're sure it's safe to move over).

Obey the Laws
When you're riding the road consider yourself a vehicle, only stay to the right side of the lane instead of in the center.  Obey all traffic signs/signals and use the appropriate lanes as well.  Same roads, same rules. 

Night Riding
The major rule for night riding is, be visible.  If you're going out for a night ride, make sure you have front and rear running lights.  Also, make sure the batteries are fresh and fully charged.  You may only plan on doing an hour ride, but things can always come up that may extend your ride unexpectedly. 
Wear bright and/or reflective clothing.  Most cycling specific clothing has built in reflective areas on it to increase your visibility.  Again, this is dependent upon the vehicles approaching having their lights on so always have running lights at or near dark!

In a nutshell, a lot of riding in a group comes down to common courtesy, good communication, and being predictable.  Practice these rules and stay safe!