How to Lead A Bunch Ride Effectively
Other than the obvious detail of where and when to meet, publishing the route ahead of time helps interested participants determine if the ride is on par with their skill level (distance, hilly, flat), if their bicycle is set up properly for the terrain (cassette size, road, mtb, gravel) and how much food, water and other provisions (a windbreaker for descents) they need to bring.
Be sure to include the estimated group speed and level (beginner, intermediate, advanced), how much time it should take to complete the course, and specific details such as a no-drop or women only ride.
Organized group rides, meant to be a learning experience, social and fun, are not meant for full-blown racers. They have their own network of buddies to hammer each other into the ground.