Give as much info about the ride as possible. That way riders know what to expect / if it will be their kind of ride.
Let as many people as possible have the GPS file of the route the group is going to follow. That way chances of people getting lost drop significantly.
Have an experienced rider, who knows the route, as sweeper. Someone that enjoys that kind of role. Having two leaders and two sweepers is a good idea in a very big group.
It is sometimes a good idea to agree on the speed the group will travel at before pulling away.
A big issue is the "experience" one, there are always going to be faster guys and slower guys. I am a big believer in smaller groups, travelling at the groups pace, not at the pace of one selfish rider.
If you happen to have a totally mismatched group you have 3 options (in order of preference):
- If you have fast riders in the group, give them the GPS route / destination and set them free. Let them go ahead and enjoy themselves. The fast riders usually are experienced riders - they can look after themselves.
- The second option you have in a big group (especially if you have more than one leader and sweeper) is to split the ride into a faster group and a slower group. That way you don't frustrated riders and potentially dangerous situations with mismatched riders. In this case the fast group will go ahead, the slow group will follow and everybody will enjoy themselves.
- The last option (with only one leader & sweeper) is to let the slow riders ride in front with the leader and the fast guys in the back with the sweeper. At every stop the slower guys leave first and the fast guys stay behind a little longer. Since they've fallen behind they can play catch-up and ride faster. If you catch up to soon, fall behind a little, catch up again, play a little. Do NOT overdo it - if you come off you spoil the day for the whole group. Rather do your really fast riding with your mates.
Never underestimate the stupidity of big groups. People loose their minds and do dumb things.