Your crop marks will be in the Postscript file that Illustrator creates. Distiller will take that Postcript file and turn it into a PDF. So you need to tell Illustrator to put the crops on the page.
You’ll need to have a Postcript printer driver installed (Distiller will work) in order for the next instructions to make sense.
Crop/registration marks are in your print dialog box.
File > Print
under the Setup tab, I usually set the paper size to Custom and make the page size 1″ larger than the document. That’ll give you room for your crop/registration marks to show up in the PDF.
Under the Marks & Bleed tab, you’ll find, well, Marks & Bleed. If they haven’t told you what marks they want, you can just turn them all on.
There is more involved that that in making the PDF, but that will get you started getting the crops on there.
I wouldn’t be shy about having your printer walk you through making the PDF, if you haven’t made a press-ready PDF before and you’re unsure of how to proceed.
-k