Points to consider when you need to do archival research:
Time: Archival materials are typically stored in a secure manner that requires time and manpower to retrieve. Allow time to explore the records of an archive's holdings and for your requests to be processed. Additionally, you will have to work with the archive to determine a date and time to make your consultation (which will likely take place in a monitored space).
Finding Aids: Archives and special collections frequently create finding aids in order to provide a guide to the contents of a collection that has been processed. A finding aid usually describes how a collection has been organized into files and boxes, making their retrieval (and your request) easier for the institution to respond to your inquiries. Not all collections have finding aids, so you might need to reach out to the archivists for more information.
Handling: You will likely we required to register with an archive and provide proof of your identity for security reasons. In many cases you might be handling rare, fragile, and/or sensitive information, so staff might give you a brief overview of how to handle and photograph materials (if photography is permitted). Always be prepared with clean hands!