After making your presence known to the sales manager and laying out the deal you want, they will attempt to bring you back to a salemen's desk and wear you down as stated above. That is when you walk out and call the SM back while driving away telling him - 'I can't believe you just let me walk out'.
I don't let them play their game. I play mine.
I have always received the deal I wanted in the first place. Refuse to deal with anybody but the SM.