I've ridden a few organized rides though not nearly as many as some people here. I can tell you a few things to avoid. First, imagine yourself good but not quite as good a rider as you are. Now ask yourself whether the imagined you would like to ride those particular roads and in that order. Would you intentionally save the 400ft climb or 12% grade for the 45-mile point in a metric century? Would you choose to ride rt.n on your own and in that direction at that time of day? Where might you get lost if you didn't know the roads already? For example, if a road changes name should the route instructions indicate a "go onto..." even if there is no sign to tell you about it? As you are riding would you like to know where the next rest stop might be? Could you bail out easily if necessary, and will you be aware of that option so you don't have to worry?

I've seen all these errors on organized rides, most on the same ride even.