Fortunately SQL Server is self documenting, at least in terms of cataloging what objects are in the database, their relationsip, usage stats, and etc. I occasionally find myself in situations where I must familiarize myself with an undocumented legacy database. Fortunately, the databases are the end of their lifecycle and my job is to either develope a replacement or at least ETL the data into a new database before it retires.

I have a collection of scripts that query configuration settings, jobs, triggers, referential constraints, object dependencies, most frequently read/written objects, obsolete objects (never read/written), etc. and then prints out a report. This will more reliably tell me what going on than what I can get out of the last guy who touched the database.