What is the best method to prevent too much of a financial loss when buying cars?

[MarketingPerson2007]

We all know that when buying a car its value will never increase, but what is the best way to prevent too much depreciation? I mean is it better to buy a second hand car every few years, or maybe a brand new car every few years? Or is it best just to buy a second hand car and to keep it as long as possible? Does anyone know the answer to this?