This is just a quick guide to using resources with links to relevant pages on the British Library’s website.
Registering for a reading pass
The first thing to do if you want to join BL is get reading pass. This is very easy to do and you can also register before you visit. There is more information online.
Searching for items
For normal searches you would use the “Explore the British Library”. For pre-1600 collections, however there are several separate specialised search engines. You can find a list of specialist online catalogues here. It is important to note however, that some catalogues only existed as printed collateral and do not have online presence. With some catalogues one must know which catalogue one wishes to consult to begin with. This is the situation with early printed collections, where one must search either the ISTC (Incunabula Short Title Catalogue) or the ESTC (English Short Title Catalogue) depending on the item searched for. Most of the Incunabula held by the British Library have not yet been digitalised, but you will still find numbers of book collections on EEBO and ECCO.
A good guide is also M.A.E. Nickson, The British Library: Guide to the catalogues and indexes of the Department of Manuscripts, 3rd rev. ed. (London, 1998). A copy is kept in the manuscripts room, although librarians are recommended to purchase a copy for themselves to advice students.
Accessing this material can be quite difficult. You will need a letter of recommendation. This would normally be written by an academic supervisor, although heads of historical societies can also sign. You also need to vouch that you have handled manuscripts before. The majority of documents are available to users (following this route). There is however, a descending level of access depending on the importance or rarity of the item. The most important are kept in the Z safe. It is very unlikely that anyone but the most qualified academics or librarians would be able to touch these items.
Interestingly you are allowed to take photos of most manuscripts. The BL have even set aside space for taking photos of large items although they do ask users to be respectful of other users.
Other sources of information
Outside of searching for items, there is a lot of information on the thematic blogs and assorted social collateral such as twitter accounts and YouTube videos.
The staff are very friendly and knowledgeable. You can always ask them if you have any questions. They even have a Quick Chat option.
If you have any questions, please go to the British Library website.