Do not send your post to more than one newsgroup. While it is allowed in some cases to post to a few newsgroups, it is safer to simply refrain from cross-posting. If the members of a newsgroup flame you for a posting, do not post a similar message ever again to that newsgroup. Treat others as you would have them treat you. Keep your signature file short.
Some people put many, many lines at the end of their message that are basically useless.
A general rule of thumb that works well is, keep the signature portion of your message to eight or fewer lines. When replying to a post, do not include the entire original post in your message. Only include the portions necessary to convey your meaning. I strongly recommend you read through the postings in news.announce.newusers before posting anything to a newsgroup. If you would like to advertise in a newsgroup, it is possible to do so while still following the rules above.