Knowing what records are out there is key to knowing how to get them. These guides will help you understand what's available and who keeps it.
Record Retention Schedules: Governments at all levels are generally required to enact rules or laws laying out what they do with records -- how long they are required to keep them, in what form and under what circumstances they can be destroyed. This "Records Retention Schedule" is itself a public record -- and a roadmap to what records are available to an enterprising journalist. This one is the State of Florida's "General Records Schedule GS1-L for Local Government Agencies." Read index and scanning the document for a window into what's available.
Investigator's Guide to Sources of Information: This 117-page guide was compiled in 1997 by the Office of Special Investigations of the congressional Government Accountability Office. Athough somewhat dated -- expecially the sections on electronic sources of information and the Internet -- it remains among the best of its kind, used both by government and private investigations. There's a PDF version you can download or an Web version you can view online.
FOI “A to Z:” Also from the Society for Professional Journalists, an alphabetically-organized list of specific subjects where FOI laws apply. SPJ says it's intended to "encourage more reporting on FOI issues" and suggests you think of it as an FOI `story tip sheet.'
Backgrounding: Reisner's concise guide.
Records are a State of Mind: From Pat Stith, Pulitzer Prize-winning reporter at the News & Observer in Raleigh, NC.