Institutional culture/politics (see also Institutional analysis)
Each institution has its own culture. It includes such intangibles as clothes and lifestyle, willingness to debate, and even whether faculty are addressed by first name by students. It is subtle and nuanced; it also varies according to who you are in the institutional hierarchy. Women and people of color find that out right away. Your best bet is to read everything you can get your eyes on, but then find an ally (see Allies). Sit down and ask the hard questions until you feel you have a handle on how the unarticulated power dynamics of the institution work. Your own intuition will kick in, but having somebody to check your perceptions against, and doing it early, will save you a lot of aggravation.