If you want to put yourself out there in the virtual world of the internet, there are some written and unwritten rules that you should consider adhering to. These rules are not meant to govern your freedom of expression or undermine any rules existing out there, it's just a mere list of things that aim to guide us in how we should behave in the internet arena.
1. Essentially when we post something on the net, we want to communicate something. Our efforts of communicating a message would be futile if the intended readers would not be able to grasp what we're saying, It is therefore important not to shorten words or use abbreviations that only you can understand and decipher.
2. It is hard to fully express an emotion when writing as compared to a face-to-face situation, but it's easy to notice a post when written in ALL CAPS, that's why it is considered as "shouting". Check yourself, would you want to shout at the top of your lungs just to express something? If you answered no, then you don't need to write something in ALL CAPS.
3. When writing an e-mail, you should never leave out the "Subject" field. If the one you are sending an email to receives more than 50, 100 emails or more each day, how can you make sure that yours will be read immediately? The only way to catch the attention of your reader is to indicate in your "subject" field the main content of your email, in the hope that the recipient of your email will prioritize reading it.
4. When writing in forums, make sure that you read first the rules governing the forum site and adhere to forum site rules. Make sure that your posts in these forums are within the topic being discussed. Refrain from posting advertisements that's off-topic.
5. Refrain from using words of profanity, vulgarity and contents that are libelous, defamatory, inaccurate, obscene, hostile, discriminatory, and the likes. One can be disagreeable but still express opinion or the likes in a respectful and constructive manner. It's advisable NOT to engage in "flamewars" - exchanging words with the intent to harm. Be kind to point out mistakes with the intent to educate and not to insult or degrade a specific person.
6. Do not share anybody's private information unless it's your own. Try using BCC when e-mailing to several people that are not in any way related to one another.
7. It is advised to not share passwords and usernames. Our security is our responsibility.
8. Post or write things that you think are relevant and verified information. Try not to post things that you yourself have not checked to be true because it can lead to wrong information going to wrong individuals that may eventually cause harm. If you are not sure about the information that you post, please note that in your post.
There are other rules out there specific for the different sites. Universally I think what is important is you regard yourself virtually by how you would be in person in a public arena.