How to set up a git project to use an external repo submodule?

I’d like to create a repo which pulls in a remote repo.

For example, let’s say jQuery as a submodule:

git://github.com/jquery/jquery.git

What would be the process of creating a repo with jQuery as a submodule and adding my own external as a remote repo.

Also once this is setup, if I push / pull to my own remote, will the external remain intact?