Assuming you’re talking to the right person, offer more than just money, and ask the right questions. Tom Chiarella lays it all out in a 2005 Esquire piece examining what it takes to become a good haggler. It’s a hilarious read to boot.
From the article: “When I asked if a price on a tube of Crest was firm, I was met with the blankness that only a haggler knows. But I found that if you ask the right questions, there are deals to be had.”