Many studios/classes have spray bottles available to clean off mats at the end of class. Spray and wipe the mat down post-practice, especially if the mat used was not your own, and put any props back where you got them.
Practicing non-violence (Ahimsa in Sanskrit) means coming into class to practice in a peaceful way. Gossip, anger, complaining and/or negative attitudes are best left at the door.
Try not to eat for two hours prior to class in order to avoid an upset stomach. Give yourself enough time to arrive at the studio/practice space, sign in, pay for class (if you have not done so online), sign a waiver if you are new, hang up your coat, use the restroom, take off your shoes and socks, and turn off your electronics. You also want to set aside a few minutes to lay out your mat, gather props, and bring your breath/mind/body to a calm state.
At the end of class, the instructor will bow his/her head and say “Namaste”. This is your instructor’s way of communicating that he/she honors the divinity in you. You choosing to reply in kind conveys that you honor the divinity in him/her, as well. This is executed with a bow of the head and hands pressed together, palms touching and fingers pointing upward, with thumbs close to one's chest. This gesture is called Añjali Mudrā.
Be sure to speak with your instructor [prior] to the start of class should there be any pertinent medical issue(s) he/she needs to be aware of. This includes, but is not limited to: surgeries, pre-existing medical conditions, physiological ailments that have recently surfaced, or any psychological distress you feel should be addressed.
Please do not arrive late or leave prior to the conclusion of class. It disrupts fellow students' practice. If necessary, be sure to make this transition as quietly and discreetly as possible. Additionally, students should respect others' space and stagger their mats accordingly.