It's simple: you just say it. But there are a few ways to go about it. Most importantly, be polite and firm. The salesperson is more likely to take you seriously if you're respectful. Also, consider making an offer that's lower than what you're actually willing to pay. This gives you room to negotiate, and you might end up getting the car for a better price than you originally expected. Finally, be prepared to walk away if the dealership isn't willing to budge on price. There are plenty of other options out there, and you don't need to do business with someone who isn't giving you a fair deal.