You need to use Mark Down Manager with eBay to discount your items.
http://pages.ebay.com/storefronts/markdownmanager.html
On the listing page, underneath where you put in your Buy It Now price or starting price, there is a box to check to "Accept offers from buyers". That will allow you to accept best offers on that listings.
There's alot of good information posted to the forums and by going to the tabs on the top of the forum...there is find. You can type in what you're looking for and it will find the answer if it's been posted to the forums previously.
Best of Luck,
Donna