When drafting public records requests, including federal Freedom of Information Act requests, it is a good idea to ask for a log of what has already been requested from the agency you are querying. Agency FOIA logs are the best resources for determining not only what has been asked for by prior recipients, but also how to request it. These logs document when a request was submitted, who made the request and, if applicable, when the agency completed its request compliance process. Click here for an example of a request for a FOIA log and the accompanying log -- this one from the Nuclear Regulatory Agency. When reviewing an agency FOIA log, a couple of things to note -- the clearer the request, the quicker the response. While many agency FOIA officers go out of their way to help fill a request, they can't read minds or find something that isn't adequately described.
Also note that a FOIA for an actual copy of a FOIA request and/or the materials released under the previous FOIA is allowed. Like requesting the FOIA log, "tailgating," is widely practiced.
A variation on "tailgating," is known as a "FOIA trap." To set-up a "FOIA trap," you place a standing request with an agency to be copied on requests and attachments fitting a certain description or received from a certain party. "FOIA traps" are commonly the hallmark of competitive intelligence professionals and, more recently, researchers working directly for the hedge fund industry.