Rule of thumb for paying below sticker price?

depends on the salesman. I'd suggest going to one of the no haggle places. They have good prices that meet the needs of both. Otherwise, do some research and find out what the dealer paid. Have a fair price in mind and make it a point to tie up a salesman for as long as possible. After 4 or 5 hours, he'll wear down and want you gone. Price will fall.