Many of the libraries and archives you will wish to visit require users to perform many steps in order to access their materials. Procedures vary: some institutions require an appointment in advance, some require a researcher's card, some charge a fee. It is advisable to familiarize yourself with an institution's requirements well in advance.
If you plan to conduct research in the summer, it is also important to check if the library will be open. Many may have limited hours, or be closed entirely for part or all of August.
You should be prepared with a letter from your dissertation advisor or department chair attesting to your research needs.
Handling the books
It is important to cooperate with the handling instructions of the libraries you visit.
What to bring with you
Be prepared to leave most of your things in a locker and have the items you bring in to the reading room searched thoroughly and repeatedly. Some libraries may allow you to photograph the material; be sure to ask if this is allowed before you start doing it, and make extra sure that your flash is off.
A site where researchers post about their experiences researching at various libraries and archives.
An archival collection guide, often called a finding aid, is guide to a group of archival records, personal papers, or manuscripts. It may be a brief summary, or a detailed description and inventory. The guide describes the origin, extent, dates, contents, topics, and organization of the records.
Archives are generally held in folders in boxes, and described in the number of linear feet that those boxes take up.
Archives Hub in the UK has a very good guide to doing archival research.
Searching for & finding archives