Show up understanding the features of the product and negotiate.
Show up knowing nothing/little, then you're on the same level of all the other mediocre salespeople & customers.
Which might render a more satisfying deal?
^^ Absolutely correct - Knowledge is money saved, show up to playball...

layball:
I setup a killer deal (Dec. 2015) on a
brand new 2015 Lexus RX350 loaded, at 13.3% off MSRP and the 2016 models was +7%$ / effectively saving +20% and still getting new:
a) I went into the dealership (alone), looking for the youngest salesman, with knowledge & ambition (hungry for the sale, and not an old-beer-belly-BS'er sales type, with an established client list, of repeat customers for decades).
b) I found the man / chit-chatted and formed a relationship / told him:
"I got a qualified customer, to hand you on a silver platter"
c) My son has his heart set on a new Audi S5, so I shared my respect for the Toyota brand (wife has a v6-RAV4 & I looking for a older Gen3 4Runner) & huge Audi dislike personally (quick depreciation & expensive repairs)
d) Salesman spent 1.5 hours with me / and was so impressed with my knowledge, he handed me a most generous 63 page Lexus Brand coffee table book (2015 President's Message), on my way out
e) 2 weeks later, son test drove the Lexus with salesman in front (explaining all the electronics) with dad riding in the back
f) returned SUV to Dealership & went straight into a 1 hour (2 on 1) serious price negotiation
g) vehicle purchased that night, the same week the new 2016 models started entering dealer showroom floors / at huge savings
^^ Let Sales Agent clearly know: "a fantastic deal (right now), or we are ready to walk, at any time (without much notice)".
- got 48 month low financing, on purchase & buy payments worked out $40/month cheaper, than a crappy 4 year lease option
- put oneself, in full control / take drivers seat, in the Sales process / after-all, Dealer wants our $$
The buying purchase, was a fun experience & very rewarding - a natural high/rush !!
- torture yourself instead, is only due to lack of true auto knowledge & real bargaining skills / & easy gross overpay results