Paleography is a complex area of study.  Please refer to the linked guides listed below, but note that enrollment in one of the paleography classes offered is recommended:

This section includes primarily Latin dictionaries, with some other medieval dialects in addition, and a general dictionary in English for the Middle Ages, as well as a bibliography of common tools.  WMU holds hundreds of printed dictionaries to suit various needs.  Consult your advisor or instructor regarding the best tools and books for the text.