Wear a helmet. Pretty much no exception when riding with amateurs.
Make deliberate movements. Being able to gradually accelerate or slow down will get you invited back to most groups. Be especially aware of this when it is your turn to take a pull at the front, and when you are pulling through and off.
Easy on the brakes! Reaction times being what they are, a few riders at the front of a group tapping their brakes indiscriminately can cause a terrible pileup at the rear. If a heavy braking situation is developing, it is quite common to hear the lead riders shout “braking” as a warning to the others. It is so unusual to use the brakes in a peloton, that this kind of warning is even heard while racing , (normally, racers will only point out road hazards to teammates, preferring to just skirt bumps and cracks themselves, in the hopes that their competitors will be unable to avoid them)!
Instead of using brakes to slow down, experienced group riders ease up on their pedals and open up their posture to get a little space. Other riders can sense these subtle moves, and make adjustments to their own speed accordingly. If an obstacle presents itself, (other than a rider down in front of you), it is best to ride straight over it. Learning to “bunny hop ” has prevented many a crash.
Ride defensively. In the end, you are responsible for everything that happens in front of you and to your immediate sides. While the person in front of you should be considerate of your safety, (such as pointing out oncoming road hazards), they are not obligated to take your needs into account. Just like when operating a motor vehicle assume liability for everything not behind you.
Don’t be overly aggressive. No one likes an aggressive rider, especially if he or she is putting other people in danger. It is one thing to push the pace constantly or to attack unexpectedly. It is quite another to make abrupt line changes, scoff at traffic laws, and disregard the safety of others.
Don’t be overly timid. No one likes a timid rider, especially if he or she is putting other people in danger…yes, being overly cautious, especially if it means using your brakes too much, can be just as dangerous as riding aggressively.
Follow the rules of the road, but be aware that other may not. When approaching stop signs or red lights at the front of a group, notify other riders by shouting if you intend to stop, slow down, or motor right on through, (not recommended). Surprisingly, many riders in New England may not be expecting you to stop if the intersection seems clear.
Avoid overlapping or "crossing wheels" if at all possible. Experienced riders seem to consistently ignore this, but be warned, crossing wheels is asking for trouble.
Leave yourself an escape route. When drafting, be prepared for the riders in front of you to slow unexpectedly. They won’t usually do this, but just in case, be sure that you can ride up past their rear wheel without actually running into it. Sometimes, you will not be able to react as quickly to an emergency as you might hope, and having a little room to bail out can save a fall. For this reason, unless the perceived wind is coming from directly in front of me, I always shade a little to one side or another of the wheel I am following. Besides putting me in a more advantageous drafting position, it gives me an escape route.
Look up the road. Avoid staring directly at the rear tire in front of you. Instead, be sure and look up the road, through the tangle of arms, legs, and bikes. Experienced riders keep station inches behind the wheel they are following by referencing how close they are to the body in front of them. We do not stare fixedly at rear tires. Instead, become “spatially aware”. It’s a bit complicated to explain, but I think of it as measuring very carefully whether things in my peripheral vision are getting subtly larger or smaller. If the body in front of me seems to be looming a bit large, I ease up a bit.
On most club rides in New England, (although not in parts of Europe), pointing out obstacles is standard practice in big groups. This is typically done by pointing down with either the right or left hand at the line the rider behind you is to avoid. This is sometimes accompanied by a shouted warning such as “hole” or “bump”. Be careful that you don’t lose control of your own bicycle while attempting to warn others. If the road becomes dangerous, no one expects you to do anything but look out for yourself. Avoid, also, “crying wolf” too often. Riders do not need to be warned of imperfections in the road surface which they could ride over or through without warning.
Whenever possible, make only very gradual maneuvers to avoid road obstacles. Do not swerve wildly at the last moment to avoid a bump. Remember that there may be riders very close to your rear wheel.
When leading a group or paceline, it is far better to take a wide gradual path around an obstacle, than to point it out with a gesture. It is better to let the riders immediately behind you get a “good look” at the bump.
In a rotating or double pace line, pull through and off predictably. Do not attempt to shirk your duty to take a pull by slowing dramatically when you feel the wind for the first time! Yes, it’s windy up there!
Also, do not veer out of the lead position after your pull until the rider who took a pull before you is clear. Many riders who feel they cannot handle a pull at the pace of the group accelerate rapidly in order to be able to pull off sooner. This is bad. Better to let the riders around you know you have nothing left in the tank. I usually say something to the effect that “I can’t add to the pace”, in the hopes that the riders in the recovery lines will ease up a bit.