There are lot of different people meeting and talking in newsgroups. It is seen as some kind of courtesy to obey some rules of manner, Some basics are listed here.
Before you ask questions be sure you read the newsgroups FAQ (Frequently Asked Questions) and didn't find the anwser.
If you take part in a discussion, be aware the fact, everybody can read the anwser. Say nothing you wouldn't say to the others when you were facing them. Avoid insults.
Try to avoid crosspostings. Do not ask a question in more than one newsgroup when you don't know which is the right one. Ask in one newsgroup. If it is wrong, you are told which is right one.
Formulate your articles accurately. Nobody likes to read an article with lots of typos, even with content worth a Pulitzer. Think of your articles as letters. Your letter speaks for you, it represents you. Somebody reading your article will draw conclusions about you from it, wrong or right.
Remember, nobody sees your grin when you are writing an ironical sentence. It may be funny for you, but it can be very serious for the one reading it. It is very difficult to include emotions in an article.
The most important rule: Use your common sense when you are anwsering or publishing an article.