False, false, false! The only way you'll catch any guff as a newcomer is if you don't use common sense and jump into things without knowing the proper procedures. As long as you know some basic information, you'll do fine on the Internet.
Just like in the real world, if you don't know how to do something, read the directions first. Almost all Usenet groups and email lists have what are called FAQs, which stands for Frequently Asked Questions. These documents will contain all the basic information you need to know before participating in that discussion group.
For example, suppose you want to participate in the fictitious Usenet discussion group Alt.Fan.Redbirds, a group which talks about your favorite rock group, the Redbirds. The FAQ for that group might have the biographies of each member (so people won't be asking the same "where was the lead singer born" questions all the time), a list of all their records, and any other basic information about the group. Having this information in an accessible document prevents discussions from getting bogged down with the same subjects over-and-over. Also, you'll find information in the FAQ about who the moderator (basically, the boss) of the group is, procedures for posting messages, subjects that are welcomed or should not be discussed in that group, etc. You'll save yourself a lot of grief by reading through the FAQ first thing!
How do you know where the FAQ is? That brings us to the second important skill Internet newcomers must have and use: the ability to ask. Just ask someone in the group, they'll tell you. They won't "bite off your head" or make fun of you because you're new. In fact, almost all discussion groups on the Internet welcome newcomers, because they bring with them a fresh perspective on whatever topic is being discussed. Just post your first message as a short introduction of yourself, along with a request for directions to the FAQ. Check back tomorrow, and you'll probably have a response, whether by email or posted in the Usenet group itself.
Read through this FAQ. If you need more help, contact the group's moderator by email. Either the moderator will volunteer to help, or you'll be given an email address of someone who can help you.
The Internet is, for the most part, a friendly place. And, if you're still nervous about dealing with the "old timers" on the Internet, remember this: they were "newbies" once, too!