A good clean car always helps. As for the exterior, if you were to wax it after you wash it that would help tremendously in the way the car looked and how easy it is to clean since wax makes an invisible barrier to the elements. As for the inside you could give it a nice detail and maybe try some window tint, you can pick up a tint kit from the parts store for like 25 dollars and just have a friend put it in for ya!