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Gordon R. Meyer
An Apple Help primer
An older article from MacTech magazine is available online at their website. I'm talking about it here for two reasons. First, it provides a good introduction to some of unique features of Apple Help. It discusses the special meta tags you can use, how searching works, and how to provide AppleScript-based automations for your readers.
However, please be aware that things have evolved since the article was written. On Mac OS X, help files are installed in an application's bundle. Also, the old Apple Guide method of installing your help menu has been completely replaced with a much easier approach. So, be sure to do a reality check using the documentation at Apple's Developer website before getting off on the wrong foot.