The process has changed a bit for exporting to dwg (or DGN for that matter). We used to be able to export our own settings to a .txt file format for use with other projects. In Revit 2011 we had this dialog and Save As button.
With 2012 they've decided to capture our settings in a project file itself. They let us choose one of these four standards to use, or to use as the spring point for our own version.
The fifth option is to "Load settings from file...". Interesting that there aren't any files to use though. We are to capture our changes in the project and then, when desired, pass it along to other projects via the Transfer Project Standards tool.
I've posted the source files that the four export settings templates use because they don't appear in my 2012 installation anywhere. I recovered them from my 2011 installation. Interestingly the other three besides the AIA version didn't show up until I loaded each one in to replace the previous. As soon as I did that, the other files appeared alongside the AIA version. If you really want to edit the .txt version, to grow your own version, you can download them here: