You can park your domains on most exchanges by just changing the DNS servers on your domain. For example, you change your DNS servers to ns1.afternic.com and ns2.afternic.com to park on Afternic.
I strongly advise having a "for sale" parked page. Buyers - like the rest of us - are lazy. If it doesn't look easy to purchase, most won't bother.
We exchanges all want sellers to park their domains with us. Whoever gets the parked domain probably gets the sale.