One of the points that gets missed in riding with a group is to RELAX. A lot of people who are new to group rides swerve and and weave because they're wound so tight that any little bump in the road sends them veering off line. Bend your elbows, breathe, and don't fixate on the wheel just in front of your wheel. Look over the shoulder of the person in front of you and be alert when the two in front point out the next hazard for the group to avoid.