Things to know - prepare for the worst
As we all know, cycling is not a risk free activity. While we do our best to ride safely, it's inevitable that incidents (crashes) will happen. Preparing yourself for a possible incident and knowing what to do in case there's an incident on your ride can prevent further injury and speed the emergency response. This is not meant to be an exhaustive nor expert recommended list. Consider it a set of reasonable guidelines that can be expanded upon.
Prepare yourself for a possible incident:
While we hope it never happens to you, it's best to be prepared in case it does. How does one prepare for a crash? By making it as easy as possible for folks to help you by carrying Emergency Contact information and any critical medical information a 1st responder should be aware of with you during the ride.
We require that you provide emergency contact information when joining the club and ask you to update it if necessary when you register for a ride. However, in the stressful environment of an incident, the ride leader may have difficulty getting that information quickly so it's a best practice to carry it with you on your ride. You can do this in a variety of ways and many will use multiple methods. Keep in mind, you want this information readily available vs. hidden in a bike bag. Also keep in mind that you could be separated from your bike and belongings in a severe crash.
Print and laminate a small card with emergency contacts and critical medical information and put it in your wallet.
Use the Medical Emergency features of your mobile device.
Use the crash features of your bicycle computer and associated online account.
Wear a ROAD iD 
This is considered the gold standard as it's highly unlikely you would be separated from your ROAD iD during a crash.
What to do in case of an incident on your ride:
1 - Prevent further injury
The first thing that should be done in a incident is to make sure the person who fell is not in danger of being hit by another rider or traffic. Position a rider behind and in front of the incident to direct/warn traffic of the incident. If no major injuries, move the fallen rider(s) and bike(s) out of the road so traffic can safely pass.
2 - Do NOT Panic
When confronted with an emergency, it is easy to panic. We are only human after all. However panicking will not help anyone. If you feel you are starting to panic, focus on breathing and staying calm until the situation is fully under control. Ask someone else to assume whatever role you were playing.
3 - Check For Serious Injuries
With any fall, even small ones, the fallen rider should be checked for serious injuries. Sometimes the smallest of tumbles can still result in something serious, so it is good to check rather than not. Most of us are not medical experts, but check for the obvious:
Neck injuries
Head injuries
Broken bones
Severe bleeding
Concussion
In addition to checking the fallen rider, check their helmet. If it's cracked or severely scuffed it's best to assume the fallen rider has suffered a degree of head trauma.
4 - Do NOT Move the fallen rider
If the person who fell has any of the injuries listed above, it is best not to move them. Moving someone with spinal or head injuries could cause permanent damage if not done correctly. If in doubt, wait for the professionals.
5 - Get Help
If there have been suspected serious injuries, get help as soon as possible. Call 911 and wait for the emergency response team to arrive.
6 - Check The Bike (and Helmet) For Damage
If the fallen rider is able to continue riding, make sure their bike is not damaged before they are allowed to do so. Check the bike for the following:
The frame and fork – no bends or cracks
Wheels – no bends and spinning normally
Tires – holds air
Brakes – fully operational
Gears (both derailleurs) – functional and shifts as required
Chain – In place and nothing jammed
Saddle – in place and firm
Handlebars and hoods – in place and firm
As mentioned above, check the helmet for any damage.The fallen rider should not be allowed to continue if the helmet exhibits any signs of serious damage. Call someone (emergency contact, friend, Uber, Taxi, etc.) to give the fallen rider a ride home.
7 - Check in with the fallen rider
Even if the fallen rider was able to continue, it's best to check in with them later in the day to see if everything is still OK.
8 - Was a vehicle involved?
The situation is more complex if it's a vehicular crash. In addition to everything above, 911 should be called to report the incident to the police. It's prudent to take pictures of the scene, license plates/tags involved, etc. and stay until the police arrive to provide the officers any relevant information regarding the crash.