The one thing I've learned about group riding is that there are few rules of group riding. Every group seems to have their own way of doing things. I've been in groups that push hard and take short 10-30sec pull, groups where a few strong guys tend to get on the front and stay, groups where the paceline breaks up and reforms multiple time throughout the ride and everything in between. If I'm with a group I'm unfamiliar with, I just hang back and see if I can figure out what this group is doing - short pulls, long pulls, going harder on hills or keeping a constant effort, riding close or more disorganized.