What FOIA request methodologies would you recommend to ensure you’re getting the most comprehensive data possible out of an agency or government body response?

One of the most productive things I've seen is to request for "data sufficient to show" rather than describing the data you're looking for. That way you have a bit more wiggle room in the space of interpretation. Another way is to just look up forms ("filetype:pdf site:yourmunicipality.gov" in google works wonders) that are online -- if filled out reports have text filled in by a computer, then that information was likely filled into a database, and the form you're looking at is a product of a multitude of SQL queries. In Illinois, Hites v. Waubonese compels an agency to run a SQL query if data is represented in a database, so being explicit about the existence of that law can be helpful. I'm sure similar can be said about other states. Also, be sure to explicitly request your data in an excel compatible format (some states legally require it).

Also, have a look at the Reporters Committee for the Freedom of Press's FOIA guides per-state. https://www.rcfp.org/open-government-guide/

Incredibly helpful, thanks for the reply. These tips will make their way into my requests immediately.

Anytime!