Check your ego at the door.  Ensembles are co-operative. Praise each other, but don't worship yourself.

Show up on time.

Be prepared - music, music stand, tuner, pencil, pick (if you use one), practice amp and instrument cord if you are an electric player.

Practice.  Hard work at home will ensure that rehearsal will be a real joy.

Respect those that brought you into the Ensemble.

If someone else in the Ensemble has a good idea, let them take the credit for it!

If you make a mistake, do not glare at the player on your left so that everyone else thinks that person made the error.

Be proud of the part that is yours. Cherish and nurture it.

Don't swear during your playing. Certain words carry rather well!