One thing that we stress on our dev wiki is that it is updated when things change.
We don't want our wiki that is intended to provide information and be a central source of collected knowledge to become so out of date that it is useless. As the code is updated, developers are requested to update any related information on the wiki.
Other than Coding Standards, we keep tips and tricks for working with our code base, setup information for new hires, and general environment information.