Drinking and driving never mix. This is especially true when participating in a group ride.
Always ride in staggered formation; it gives you an extra margin for safety.
Make sure your vehicle is in good operating condition. For example, a bad tire could cause an accident on a group ride.
Being too hot or too cold can also affect how alert you are as a driver. Be sure to pack appropriate protective clothing, such as a long-sleeve cotton shirt (for protection from the sun), helmet, eye protection, leather jacket, gloves, etc.
Always ride with your headlight on; it's a law in most states. Cars have enough trouble "noticing" motorcycles; riders should do everything possible to help them out.
A group of motorcycles is not considered a single vehicle. Be courteous and allow cars to enter and exit the highway and change lanes. Generally speaking, a car will not want to ride in the middle of a group of motorcycles and will get out of the group as quickly as possible.
Familiarize yourself with the route and scheduled stops.
Arrive to participate in a group ride with a full tank of gas.
Now, take responsibility for your riding, learn more ... and go enjoy yourself.