Dress in proper attire as stated in the dress code and come prepared.
Don't chew gum or bring food or drinks (other than a closed water bottle) into the studio.
Never wear dance shoes outside the studio or wear street shoes in the studio.
Don't wear dangling or sharp edged jewelry.
Leave your stuff in the waiting area and not in the studio.
Don't come late, and if you do, enter very quietly.
Don't leave early. If you must, then please speak to the teacher before class begins. If you have an emergency, exit class as quickly and discreetly as possible.
Don't talk while the teacher is talking.
Leave your cell phone on silent and in your dance bag in the waiting area.
Respect the personal space of others. Also respect the dance space. Pick up trash, your clothes, and don't turn things off or on without permission.
Don't hand or slouch on the barre or anywhere else. Be attentive at all times, especially when waiting your turn. Be aware of negative body language, like folded arms, and never sit down unless you are asked to do so.
Habit for most dancers.
If you are late, don't apologize until after class. Wait for the okay from the instructor and quickly enter and find an inconspicuous place to warm up and participate.
If you are sitting out or sitting out, sit tall. Don't lie down.
Develop spacial awareness and demonstrate it.
Give the instructor space, but not too much space.
Avoid the front unless you really know the combination.
Refrain from correcting others (that is the instructor's job).
Don't quit in the middle... of the room, the combination, the class. Go with the flow even if you are lost or confused. Don't stop traffic.
Part like the Red Sea when exiting. Don't cross center or the paths of other dancers.
It's okay to mark combinations while you wait for your turn as long as you are out of the way.
Do not repeatedly leave the room and come back without permission.
At the end of class, applaud or thank the instructor and musician (if there is one).
Don't visibly yawn or show boredom.
Good to know:
Bring a towel to wipe your sweat off the floor and/or barre.
Don't take a class way above your skill level. If this mistake is already made, do your best, but stay out of the way of other dancers.
Never walk out of a class or go sit down because it is too hard or you feel frustrated. This is considered rude and you are branding yourself as a quitter. "I can't" is not in your vocabulary.
Applaud for demonstrators.
Once you have claimed a space in the center or in a group, it's generally yours for better or worse. But don't be pushy or try to reclaim a spot if yours gets taken.
Restrain movement in a crowded class until broken into groups. If you bump into someone apologize quietly.
Never give your opinion on choreography to an instructor or choreographer unless specifically asked.
If you want help with something that will take more than a minute or two, do some research on your own and/or schedule a private lesson with your teacher.