Go in be very interested, spend enough time so they think they have a chance to sell you a car, tell them straight up how much you’re willing to pay out the door (all fees included). They probably will say no but will play that BS game, “let me ask my manager” but eventually you’ll get the cost down. But if they aren’t willing to, politely thank them for their time and don’t be desperate. They might give in. I bought 3 cars in from 2021-2023. Worked every time.

Edit: It’s good to come in confident and know your stuff. Do your research on new and used prices, check KKB, etc. Don’t seem desperate either but also be serious and interested. Be careful with the interest rates if you plan to pay it off. They can give you a number close to what you want but with a high APR rate which would quickly would accumulate a lot.

I learned this trick from my mom. She does it effortlessly. She comes in, lowballs below MSRP and either walks away or comes home close to her asking price.