Assume the existence of folklore among your users
One thing I assume about how our users deal with the local computing environment is that there exists a significant body of oral traditions and folklore around (at least) the graduate students. When you think about it, this is inevitable; when new graduate students show up they are going to ask the people around them for help, and that's the older graduate students.
(This gives you oral tradition; you get folklore because there's no guarantee that the information the older graduate students will pass on is correct or current.)
It's important to remember this when planning changes, because we can't assume that changes in how to do things will propagate around the grad student population instantly. The new ways will have the advantage of being written up in various places and working (hopefully), but they are still going to have to fight to displace old traditions, and it will probably take significant time.
(And your new ways had better actually work, and effectively, or they do not really have a fighting chance. If the new procedures are in practice ineffective, they are probably not going to displace the old ones, most especially if the old ones work at least as well as the new ones.)
I also think that it's useful to try to work out just what oral traditions are circulating around. It's hard to get good answers by just asking people, so I think you mostly need to infer the folklore from the odd things that your users do.
One reason that working out existing folklore is useful is a corollary to the existence of folklore: the less the folklore has to change to be correct, the easier it is to do it.