Public records are records of public business done by various governmental entities. These records are generally internal and pertain to the governmental body and its work. In the US, there are laws that regulate how the public can gain access to these materials, at both the state and federal level.

• At the federal level, the Freedom of Information Act or FOIA, enacted in 1967, governs when, what, and how federal executive agencies must give access to their records to the public. FOIA only pertains to the executive branch agencies; the office of the President is regulated under the Presidential Records Act (PRA), while the Congress (legislative branch) and Judiciary do not fall under FOIA.
• At the state and local levels, many states have varying PRA and Sunshine laws.

FOIA/PRA/Sunshine law requests can be simple requests for individual known documents (eg "Navigation channel improvement of the Alto Paraná River, Argentina and Paraguay : peaceful uses for nuclear explosives") or complicated multi-year affairs involving complex data over many hundreds of jurisdictions (like Stanford’s Big Local Project). 

While the exact steps vary based on the type of request (FOIA vs. Sunshine Law) and the scope of the request (requesting one document vs. thousands from multiple agencies), here is the basic process:

1. Identify the agency who would have the information.
2. Find the retention schedule for that information.
3. Locate the appropriate statute.
4. Draft the request.
5. Submit the request and wait.
6. Decide what to do if the request is denied.

• The art of access : strategies for acquiring public records [2020]

• The Freedom of Information Act (FOIA): A Legal Overview, Congressional Research Services (Aug. 2020).

• Luscombe and Walby. (2017). Theorizing freedom of information: The live archive, obfuscation, and actor-network theory https://doi.org/10.1016/j.giq.2017.09.003