Talk to end user's if possible to understand how they view / use the software. A casual chat or explanation of a bug that irks them is handy. Documentation aro

Talk to end user's if possible to understand how they view / use the software. A casual chat or explanation of a bug that irks them is handy. Documentation around batch , down or up streams is important. Tell them about any dodgy piece of glue code that the entire system relies on, can't be replaced (Because Dave left) and is to costly to refactor. And as you mentioned, fixing a small-ish bug in the system. Introduces them to the code base, the release process and any red tape.