Netiquette is a series of rules of online etiquette and behavior we practice to ensure good and positive communications. These rules help us minimize mistakes and misunderstandings.
Golden Rule
The first netiquette rule is the "Golden Rule" of "do unto others as you would have them do unto you." In other words, think about how you would feel if you were the recipient of a message and then carefully craft your writing so that your message will not be insulting or disrespecting of another. If you would not be willing to speak your thoughts into a microphone in a crowded auditorium, or post your thoughts on a 20-foot tall billboard outside your home, then find another way to compose your message. Don't be afraid to be honest, but be honest in a constructive and positive manner.
Never get into a "flame war" in which you start trading insults back and forth. If someone posts a message you feel is insulting to you personally, then privately email that person to let them know that you disagree and that you would prefer to have them be more respectful of your feelings in the future. Do this privately -- no one else needs to get into that conversation.
Also, realize that some people are very offended by vulgar language, and in a professional setting, vulgar language is not acceptable. Don't use it even if you think it is appropriate.
Be Clear
Language is important, so be specific. Make sure that anyone reading your message knows exactly what you are writing about and will not have to guess. If you are making several points in one posting, make sure to signpost your thoughts by using headings. These short phrases introducing the change in point will be much appreciated as others are reading your messages.
Also, if you expect someone to follow-up, you should specifically ask them, such as "Ann, could you please post the statistics about netiquette from the article you mentioned?" This way a specific person is asked a specific action, and your request will be clearer to all.
Be Humble
Are you an internationally known expert on a particular topic? If so, you can speak with credibility. If not, then realize that your idea might be right, or it might not be.
Back up what you are writing with evidence, either from the course materials, from other research you have done, or through documenting your personal experiences.
If someone disagrees with you, realize that they have a different set of experiences and knowledge, and avoid the temptation to get into an argument over opinions (isn't everyone entitled to their own opinion?).
Be Concise
Respect your classmates' time by learning to get your points across in as few words as practical. We are all proud of our thoughts, and we may be tempted to write several pages in one session. However, others looking at your post might think "look at how much I have to read!" You will be more effective as a communicator if you can carefully think out the most important points and synthesize them into the fewest amount of words.
Resist the Urge to CC:
CC: stands for carbon copy (or nowadays, courtesy copy), and it refers to giving copies of a message or email to more people than just the intended recipient who is being asked for an action.
Too often students will "CC:" classmates on messages as a "heads-up" -- which results in clogged email accounts which everyone needs to spend extra time managing.
"What is the big deal -- they can delete my message if they don't need it!" Well, it is a big deal, because if you and a hundred others like you are copying extra recipients on email messages, that might be an extra hour or two a day reading through extraneous email.
Be a Good Online Citizen
If someone asks a question to which you know the answer, be willing to jump in and provide assistance. Share your knowledge and insights, and help others feel encouraged to participate in sharing their knowledge and insights as well.
Respect other people's privacy. Anything posted inside the course site is meant ONLY for members of the class. Don't copy and paste comments and use them anyplace else. If something is sent to you privately through email, don't forward it to another person unless you have permission. The quickest way to lose another's trust is to break a confidence someone has shared with you.
Be forgiving other mistakes that others make. If you care to point out a mistake, do it politely and privately (through email) so as not to embarrass the recipient.
Respect Copyrights
If you didn't create it yourself, then you don't have the rights to use it without permission.
If you wish to direct classmates to a video, image, or article online - please provide your classmates with a hyperlink to the item (instead of making and posting a copy of the item). Linking to the location where something exists is not a violation of copyright (you are not actually copying the materials), however, copying and reposting the material is a violation.
This protection also extends to articles, texts, course and instructor materials, and even email. If you didn't create it -- you should not share it without permission from the author.
Avoid Sarcasm and Signpost Humor
When you are online, your classmates cannot read your expression or your body language. You are encouraged to use humor, but try very hard to avoid using sarcasm. (When written - many people will think your comments are sincere rather than funny.)
When using humor, it is often helpful to others if you signpost your points. For example:
(joke) Mathematics si 50% formulas, 50% proofs, and 50% interpretation.
"I figured that my raise this year will be about a nickel. (sarcasm)"
Using these types of singposts will help people know when you are trying to be funny and then assume at other times you are being serious and sincere.
In most situations, your assignments will include a detailed list of requirements (sometimes called a grading rubric). A grading rubric explains how your instructor will determine your grade on the assignment. The rubric contains a list of categories relating to the learning objectives, and for each category, your instructor indicates how well (or poorly) you completed the work. 
