Look around other dealers inventory (many times too high of a asking price) and sites such as Craig's List. Use a search engine to look up your model TH to see what others are selling them for.
Have realistic expectations. Dealers won't give you that much as they will try to resell it at near market value and still make a profit.
Something to think about, TT values drop massively as soon as they leave the dealers lot. Values vary widely depending on region in the country. My used TT was $5K less in NY than here in southern PA. Bottom line, price it less than the listed price from a local dealership. Be willing to go lower...maybe much lower.
2000 Cherokee 29BH with 6V batteries, LED lights & 400 watts of solar power, flipped axles and raised. 2007 Tundra 5.7L DC-LB with lots of mods. C-co, 8/158th AVN Maint.