Even though I'm not Clifton, let me add to what bigfred said about group riding - don't overlap wheels. If your front wheel overlaps with the rear wheel of the person ahead and they make an unexpected move toward you, you can be on the pavement in a heartbeat. The best way to avoid that is to make sure you don't overlap.
Group riding is an acquired skill and the first few times you do it you'll probably be nervous. That's OK, but don't let it cause you to hold the bars in a death grip - stay relaxed and focus on the rider ahead's hips and shoulders, and what little you can see ahead past them, and not on their rear wheel. If you sense that they're slowing, soft pedal or coast to slow down yourself - avoid sudden applications of brakes unless you're coming to a stop, or if it's the only way to avoid a crash. Pay attention to the group's use of hand and voice signals for things like slowing, stopping, turning, cars up and back, and for road obstructions and join in to warn others when you see these things yourself. There's little chance of over-communicating.
When it's over, you may well feel exhausted physically and mentally, but you'll also feel exhilarated.