How do you document your databases?

I find that most of my clients are not documenting their databases at all and I find that pretty scary. To introduce some better practice, I would like to know what tools/process people are using. * How do you document your database? (SQL-Server) * What tool do you use? * Documentation Storage Format for database schema/meta-data? * Word documents * Excel spreadsheet * Plain Text * Documentation process or policies? I am not talking about reverse engineering / document a existing database, but mainly on the documentation best practices while you develop your system/database.