Wash, wax, clay bar your car once a month, or once a fortnight.

I tend to rinse my car once every 2 or 3 days, when i actually drive it, just to get the dust off. I'm also pretty anal about where I park the car, I don't usually just go park it anywhere. But my paintwork is fuxored anyway from the previous owner. My old hatch was immaculate, only 4 chips in the whole thing, and I knew where every one was.

Interior wise, just make sure u clean it/vacuum it regularly. I carry these wipe thingy's so i can clean the dash and shit, also have a electrostatic cloth, for dusting the dash, that i leave in the glove box, and i just use it out when im waiting for the traffic lights to change or something.

Engine is simple, servicing, regular oil changes (ie: every 5000km's) dumping fluid's, also good driving practices. Wait for the car to warm up before u decide to do limiter launches or rev the tits off it. Even still, these sorts of things will cause wear and tear, but its why we own WRX's