I had the privilege in graduate school to study Architectural History with Henry Glassie, one of the founders and leading figures in the study of Vernacular Architecture.  He served on my dissertation committee, and I took several of his courses, including Seminar on American Architectual History, Fieldwork, and Material Culture.  Within the first couple weeks of the Seminar, he had us out drawing old buildings, studying them up close, examining their construction and materials and interior volumes. Below are some examples of my notes from the Seminar (1994) and from Fieldwork (1997).  The notes are very crude as it was really hard to keep up with Henry!  But it was worth it; I've been using these methods ever since.