Try to eat at least two hours before class. If you must eat something, try a few pretzels or yogurt. Pack an energy bar or granola to eat after class.
Try to use the restroom before class.
Be on time.
Stay until you are dismissed.
Notify the teacher if you are ill, injured, or pregnant. Some poses or practices are not appropriate for all conditions and modifications may be necessary.
Turn off cell phones, pagers, and blackberries.
Be quiet.
Clean up your area before you leave class.
Respect the sacred space of the studio and your neighbors.
Take time after class to think about what you did in class and how it made you feel.
Don't
Allow yourself to get dehydrated.
Wear clothing that is too restrictive or too baggy.
Eat a heavy meal right before class. The dynamic movement and tendency to invert works agains the upper GI... ie, you might get sick to the stomach.
Be disruptive and ask to go to the bathroom during class. Just go if you have to.
Be late. The first five minutes of class are often the most important.
Leave in the middle of Savasana. This is poor yoga "etiquette" and disrupts others' attempt to relax.
Ignore your body signals (pinching or burning pain, breathlessness, dizziness, nauseau, or cramping). These are indicators that you need to modify or stop what you are doing.
Talk on the phone or text during class. If you MUST take a call, quietly leave class.
Disrupt the class if it is not an emergency. If you have a less than urgent question for the teacher, see her after class.
Leave your mat or belongings. Carefully roll the mats and props you use and replace them as you found them or better.
Walk over or step on another student's mat. For the duration of class that is a safe and sacred space for them.
Rush out of class without taking a breath or two to enjoy the benefits of the practice!