Where to place the admin screens for a module When developing a module with an admin-area, what are the guidelines for menu-placement?

There is admin/settings/*, admin/structure, admin/content and so forth. 

From what I can see, most modules follow arbitrary guidelines and often clearly content-related pages end up in admin/settings/foobar, or pages that have little to do with the architecture of the site end up under structure.

What are rules-of-thumb? What are the guidelines?

For example, I have a module that renders a tag-cloud, and I have some settings that allow manipulating how this module renders its pages. Settings such as "what vocabularies to include" and "amount of tags to render".

From a user POV, I would expect the first setting under admin/structure yet the other one under admin/config/user-interface. But I'd rather keep them together; since I believe a user (1) installs and then (2) immediately configures this type of module, once.
There is a handbook page that covers where you should place these menu items.

See Information architecture

I won't copy and paste the info here as it is too long. You also don't provide any info on what your module is about, so I can't even paste a excerpt that pertains directly to your issue. 

The handbook page should be considered the canonical source for this info.

EDIT:

While these are guidelines, I don't think that they are very cut and dry. I would personally place the menu where the other two major tag cloud modules (Cumulus and TagCloud) place theirs: admin/config/content and keep them both in the same spot (one as a child item of the other)