If this commandment is not heeded, you will quickly find yourself alone, and will, in all likelihood, not be invited to return. Thou Shalt Be Tactful. People are different, some have grating personalities while others are lamb-meek. Believe me, a sure-fire method of losing respect within the group and forfeiting your welcome to return is to accuse another member of stupidity. You must remember, not all members of the same group will have equal skills.
Some authors excel at dialogue, some at description, some at plotting . . .
Use your head, think before you laugh at someone's clumsy prose, and by all means, talk to them as you expect others to talk to you. Thou Shalt Not Participate With A Closed Mind . There is nothing more infuriating than an author supposedly seeking advice who is not willing to take any. But Be Thankful. The authors in the group are volunteering their time to help you develop your craft.