I have often been shocked at the lack of customer service in group exercise instructors, not just Spinning, but all modes. I have been to many classes where the instructor was in such a hurry to get the class started he or she did not even introduce himself or herself, greet new students or give an overview of the class.
I recently taught a lecture about customer service and to prepare for that lecture, I looked at large companies like Wal-mart, McDonalds and Disneyland to see what their customer service policies are.
Overall, it is extremely important to acknowledge people both when they enter your business and when they leave, smile, be friendly, offer assistance and when there are problems, apologize quickly and solve the customer's problems as soon as possible.
If we apply this information to our group exercise class environment, we should greet our students before class begins, smile, help them with equipment and be willing to roam the floor to solve any problems that arise during the session. At the end of class, we should give positive feedback, assist in putting equipment away and thank everyone for participating.
Customers who have positive experiences from the moment they arrive to the moment they leave will not only be back but they will advertise for you.