What do we know? / What don't we know?
Get used to not knowing everything, and to making very clear distinctions between what we know, what we suspect (and on what grounds), what we guess (and on what grounds), and what we don't know (and why). The study of manuscript books, like the study of almost any work of Medieval art, proceeds in a mist of uncertainty. Great scholars, whose work you will read, will openly declare at various points that the manuscripts they are working on have baffled them. This is not wasted effort. Declaring that a problem exists helps to define the tasks of the next scholars who examine the document. Each of us benefits from the small progress made by those who went before us, and each of us adds something to what the next generation of scholars to work on these problems will have at the start. Share your results with your class colleagues! Start a public folder post as soon as you get your manuscript leaf assignment and start recording what you know, what you suspect, and what you do not know. Look at others researchers' posts, learn from what they have discovered, and help them answer their questions.
If you are working with an Early Modern or Modern document which reproduces a lot of standard information in standardized format, think about how and why that developed from Medieval scribal practices. Here are some things Medieval manuscripts often do not have that even hand-press-era printed books usually have:
Think about the interpretive advantages each kind of information offers the analyst and interpreter, and be thankful every time a manuscript offers you even one of those kinds of information. And be frank about noting what puzzles you about the text.