Project 1989,
as I used to work in a shady dealership a long time ago, here are some of my advices:
don't drive to the dealership with you trade in, have relative or uber drop you off.
be polite, smile, know exactly how much you want to spend out of the door.
Say no to every dealer Add-on, politely, even if you say no, they will ask again during financing
once you are done with sales and agree on a price, then bring in your trade.
more time consumming but worth it.
get your financing done prior.
by doing this, the only thing you are really negociating is the price of the actual car:
here is a good 2 minutes read:
https://consumerist.com/2007/03/30/...ff-with-the-four-square-heres-how-to-beat-it/
in the end don't be unrealistic either, for example comparing some B.S advertised price that have fake discount and added rebates that no one qualifies for....
If you want to buy pass all of this and the new car delivery process, just buy a slightly used model at internet price like we did. 34900 for our suburban LT plus taxes...
Have fun!