USENET was one of the first forms of digital networking that was accessible to regular people. Because it's been around for so long, it has a tremendous number of groups-called newsgroups-on it. In fact, there are over 100,000 USENET newsgroups in existence. The sheer number of groups can make things confusing for new users. To that end, the USENET system is divided into hierarchies that can provide you with some indication of what the groups are about. Here are some other ways that you can make sense of this very impressive and large scale system.
Check the Group's Articles
For a moment, imagine that you're looking for astronomy groups. Logically, you go to sci.astro for some good conversation. When you want to branch out, however, you may find yourself at a loss to differentiate the good groups from the wastes of time. The first thing you need to do is read the posts on the new group. Check for spam posts. If there is a lot of spam getting through, the group may be unmoderated, which means that you're going to have a lot of junk to sort through to get to the good stuff.
Read the Conversations
If there is not a lot of spam, read the conversations. Usually, on USENET, there are some fairly intense conversations going on. Check the references that people are citing and pay attention to their language. Are they actually citing scientific and reliable references? Are their conversations interesting an informative or are they all just trolling each other? Read the posts to determine all of this.
Is it a Clique?
There are some groups that have a few active posters and almost no one else. These newsgroups get tiresome quickly as they're really just conversations between the regulars. The Big 8 hierarchy groups tend to be the best in terms of welcoming new people and, at the same time, managing to have expert participants who offer great insights and information to the conversation. Post an introduction and see if anyone says "Hi" to you. If not, you may be looking at a dud of a newsgroup.
There is such an incredible number of newsgroups out there that it makes no sense to waste your time on ones that are not engaging or fun. Take a look at each newsgroup and decide for yourself if you'd like to join based on what actually happens on the newsgroup rather than based on the name.