Depends on the real price of the car and popularity of that model. First and foremost, before you walk into the dealership you should know the cost to the dealer of the car you're interested in. Not the sticker price and not the invoice price, the REAL price minus dealer holdback and whatever incentives are active at the moment on that make and model. That will be well under the invoice price. That info is available online and you should be able to find it so you know your starting point.
Once you have the numbers, it comes down to supply and demand. If the model is not in demand and there is plenty of supply, you should be able to easily negotiate a price well below invoice. They'd rather sell a car and make $500 rather than to not sell a car and make $0 and that should be the way you negotiate it. "Yo, sticker on this car is X, the invoice says it costs you Y, but in reality this car costs you $Z with incentives and holdback, I'll give you $Z + $500. You can make a $500 profit or I'll buy at Dealership Q and they can make the $500 and you make nothing. You have 2 minutes to approve the deal."
If the car is in high supply and/or low demand that will work every time. They want to cheat you, but if they can't a small fair profit is better than no profit at all. They'll take the money and try to screw the next guy even more to make up for it. However, if the model is in high demand, short supply or they get an allotment and can't sell more than a certain amount per month, you're out of luck. The leverage flips and they'll tell you to pound sand because they can make $3000 profit off some other schmo and they'd lose money selling it for less than that.