Create Simple self-approval Criteria workflow

We want to implement Workflow for UCM, to allow the contributor to perform a self approval of the content before it is published.  We realize that to do this a criteria workflow is needed.  How can a default criteria workflow be created that allows the contributor to do a self approval?  We are stuck on trying to define a global condition.

Is there an existing  metadata field used on every document by default?

Do we need to create a new metadata field?

Is there another way to do this besides using metadata fields?