If you are financing through the dealership, ask what is the total amount you are paying for financing. This is often the difference between what you are paying for the vehicle and what you could get the vehicle for if you were able to come in and pay cash. Sometimes trading or not trading in a vehicle can impact your financing charge as well.
Don't leave the dealership until you have the loan signed and finalized. Some dealers will quote a rate, allow you to take the car then contact you to let you know the rate is now different. They are counting on your excitement with the new car to push through this higher interest rate.