This is going to be an interesting topic. Which threads (on your forum) attract the most attention and, in return, receive large amounts of activity? Are the topics of these threads related to the subject matter of your forum, or are they based around off-topic subjects?
In addition to that, a lot of them are off-topic "post your ____" type threads. Such as the music thread where you post what you're currently listening to or a niche topic on AA would be posting a link to your forum, for example.
