You can add an outline to an object with the Ink Bottle Tool
Note: If you want to outline text you must first break it apart (Command-B or Modify > Break Apart) so it becomes an object. If you want to outline (or add a "stroke") to a symbol you must double-click it to edit it.
In this movie you see how to position the Ink Bottle Tool to add both an inner and outer stroke
To remove a fill you must first select it then delete it