Once you find the car you want, you'll want to move fast so it isn't sold out from under you. So it's a good idea to get your financing set up before you begin searching for your car. If you're paying cash, there is little to do except make sure you have the funds available to withdraw cash or get a cashier's check when it's time to do the deal. If you're paying all cash for a used car from a private party, consider doing the deal in a public place.
There's a big safety benefit to buying the newest car you can afford. When you buy a new car, you're ensuring you're getting a car that's up to the most recent safety standards in both crash testing and in safety technology. A new car compared to a used car from even five years ago can have big safety advantages with things like more airbags, a more rigid construction, and more advanced technology like a backup camera which is now mandatory on every new car sold in the U.S.