What is the best way to drive your car to avoid damage or retain it's condition?

I am buying a new car today and want to make sure that I don’t damage it by the way that I drive.

Is it bad for the vehicle if I coast down hills with my foot on the clutch or is it better that I ring it out in a lower gear and a rev count of about 3 or 4k? (manual transmission of course).

I have always rolled down hills with the clutch in but was told this wasn’t good for the car but it always sounds like I am damaging the engine when I drive it down the hill.

Does anyone know and can anyone offer any tips to drive the car in a way that is nicest to the car?