How do I select the right forum?

Are the forums defined anywhere, formally or in-? For instance, if I’m soliciting stories and opinions on a subject, is that a GQ or a GD? It’s hard to imagine an IMHO that will not lead to a debate, so how do you decide where to start?

The main page of the SDMB has a forum description for each forum under the links to the forums.
Stories on a subject would generally go in MPSIMS, but if you’re asking for opinions on said subject, that would go in IMHO.
GQ is only for questions that can get factual answers.
GD is a little bit more gray. There are questions or types of questions that have been going for a long time. Topics might move into there if they turn into great debates (I don’t frequent it as much, so maybe someone could help me out here).
IMHO questions sometimes lead to a debate, but definitely not always. IMHO can be a place to post your opinion on a subject and see what others think without there being a clear debate.

The silent one is correct. I will make an additional distinction between IMHO and GD, though. GD is for topics that are generally more heated, religion, politics, economics, etc. IMHO is better suited to more light-hearted topics, like the best rock-n-roll band, mayo vs. Miracle Whip, the best way to shine your shoes.