I’ve noticed some posts are putting a lot of tags. Just so you know, Discourse was built by people who dislike tags and never wanted to have them. Tagging was only added as a plugin and is entirely optional. So the way the site works it mostly ignores them.
The only thing tags are useful for is for adding a way of classifying things that cuts across categories. If, for example, there are both talks and articles by a certain teacher, adding a tag of the teacher’s name can help find all these. However, even in this case, if the teacher’s name is mentioned, search does just as well.
I use a tag for my series of essays on my ongoing translations. That’s because I post a lot, so not all my posts are to do with that, and there is no simple search field that can easily group all these in one place.
So when you’re making a post, if there is a specific need such as this to add a tag, great. However, if search + categories does the trick, there’s no need. But if you just like tagging things, have at it!