Categorize topics. Move topics in the right forums
Categorize posts. Move posts from one topic into the more fitting one. Move posts into a new thread
Communicate with users who go against forum culture (forum rules). If all fails, ask users to not interact in the forum any more.
1. topics. Influence where the discussions go. Create activity within the community
2. answers. (posts). Answer questions you can answer
- create an community where users feel comfortable.
point content to the people who can answer them.
If your community is selling products, market this with all available tools mentioned above.