I'm looking for a document template and some writing/style guides to structure the content of a Developer Guide for a subsystem I am about to hand off to a client. This goes beyond documenting the public API - I want to walk developers through an easy process of writing a client for my subsystem, teaching them the API and other things they need to know in the process.
I'm looking mostly for content, structure and style guidance, so references to this or that tool should be considered in that context. Come to think of it, a reference to a great example of such a doc/resource would be just as good as a "template".
Thanks in advance.