I am a retired new car dealer. I have sold tens of thousands of cars and trucks. You can do it one of two ways. You can spend hours and hours on-line researching prices, hours in showrooms haggling, and listening to hundreds of amateurs all of whom bought the car or truck much cheaper than you ever will. Or, you can go to Costco and get their list of participating dealers of the make you wish to purchase after you have looked at a variety of them. They will give you a reasonable price that will not be the cheapest in history but will be very competitive. It very much depends on what your time is worth!
Remember...many people will always tell you they got a much better price even if the dealer decides to give it to you!