Some things to think about... call them tips, call them ettiquette, or just call them garbage. Your call, but hopefully these are some things that make you think.
Establishing a Route
Decide the route the day before and distribute it in advance so people can be prepared
If it is windy, plan to ride into the wind for the beginning, and plan the route accordingly
If it is a hilly route, try not to put the big hills in the beginning as it will kill morale for the less accomplished riders
If the weather looks like it might turn bad, consider a circle route with parts that allow for cutting the route short if necessary
Leave on time
Lead rider should try to keep their effort constant
If going up hill, don't maintain the pace, maintain the effort
If going down hill, pick up the pace to keep the level of effort constant
If the pack is intended to stay together, keep the lead rider informed if gaps are forming so that they can correct
Don't drop your effort when you are taking a drink, practice doing so without "pausing"
Same with getting out of the saddle, do it on a downstroke to prevent pushing the bike back
Practice looking back over your shoulder without drifting. Tip, drop your opposite elbow/shoulder when looking back and it should help keep you going straight
Hope you find this useful!