Letters / Job Portfolio: What do I include? [7]

I've looked online; I've asked friends and family. I've consulted with some employees/volunteers at the work-force center, and yet I have not been able to get a solid answer for my question: What do I include in my portfolio and how many peices do I show?

I am a writer, and I'm investigating positions in the local media in town. I'm not sure what core peices to include. Do I put forth just essays and articles? Maybe I should add a few poems, a couple chapters, or short stories? And how many works do I include?

And other than my own work, what else do I include? Do I include a resume, references, a cover letter (or, along the same lines, an introduction), an "about the author" section, letters of reccommendation, or something else that could be note-worthy?

I'm just slightly confused on the subject. Any help would be much appreciated.