There are any number of awesome guides to group rides out there. As opposed to re-inventing that particular wheel, we are posting some links to those guides  for your edification!

http://www.bamacyclist.com/articles/groupridetech.html

http://goo.gl/SlkFJO

http://www.active.com/cycling/articles/basic-skills-for-group-riding

One day we will write our very own guide to group rides but for now you can check these out as well as our FAQ about our training rides.