Reading Usable Help
@UsableHelp on Twitter
Gordon R. Meyer
Implementing Apple Help screencast
Matt Neuberg has made a brief, but comprehensive, tutorial movie about how to implement Apple Help for your Mac OS X application. The movie isn't long, but he touches on most every subject you need to know, including complete coverage of the basics.
I'd only add that specifying an AppleIcon is not required, but is a best practice. Also, storing your help files in your application bundle Resources directory is recommended. And if you're going to provide more than just a page or two of contextual help, AHLookupAnchor is a better choice than AHGotoPage because the latter can break if your HTML file names get changed.
But all in all, his movie is a good introduction and a nice alternative to reading about Apple Help.