Graphical representation and navigation of Categories and Topics

Could use a little guidance on original Topic Posts. I am helping set up a new forum and working out habits for a group of neophytes such as myself. It seemed to me that the original Topic Post should be short and simply introduce the subject and then subsequent replies would be the substantive ones. Is it typical for the original Topic Post to launch right into a complete first discussion or statement concerning the topic? What is good practice on this. I think I’ve seen both styles as I’ve meandered around Discourse forums.