Here's the real strategy:
Don't lure them into thinking you'll finance, but simply negotiate the lowest possible price (to be done AFTER you secure a written offer on your trade in, if you have one), THEN discuss payment options...if you suggest financing right away, they'll usually just speak in terms of monthly payments, which isn't what you want...so no need to trick them into thinking u will/won't finance, get to that later BECAUSE the salesperson is NOT the person who'll talk financing with you anyway.