Just a quick note for those lazy as I am. Roland Weigelt’s GhostDoc for Visual Studio 2005 and 2003 is a real time saver. In short it installs as an add-in for Visual Studio and will add XML documentation to your methods in your code.
It is very customizable and just works. If you find it teadious to always have to write documentation for your methods as I do you should check it out. It is as easy as a right mouse click and choose "Document This" in your code and done. It also rewrites documentation for methods whose parameters have change.