Know the Facts
You should first of all know which car you are looking to buy, particularly if you are buying a brand new one. The prices are available online and you can know the invoice value easily for a particular car with particular specifications. This gives you a wide range to play with. In case of a used car, you can check the value of the vehicle on kbb.com (Kelley blue book.)
Keep a Range in Mind
Know what price range you want the car to be in. Your monthly installment will depend on the price, your credit beacon score and for how long you finance the car along with the down payment you make. Have a rough working for all these aspects and know how much you will approximately be paying.
Stick to Your Guns
Car sales personnel are highly skilled professionals and know how to talk the customer into their terms. Listen to them and let go of most of it unless it is something that you can use of in later negotiations.
Do not get all excited and angry as this will most likely play in the favour of the dealership. Remain calm and keep on negotiating until the price comes into your preferred range.
Never Give too Much Information
This is particularly important if you are selling a vehicle. Never mention the ills of your car, which can decrease the value of the car. Also visit kbb.com to know how much your car is worth. Dealerships often lower the price on a new car as per your liking before ripping you off in the trade in.