Exterior:
Frequent car washes and waxing. Clay your vehicle 2x a year to remove the really sticky stuff. I use a cleaner wax most of the time. Use underbody washes to rid your car of salt grime after snowstorm.
Interior: Leather cleaner and conditioner on the seats. I do this once every 2 months. The driver seat cover, side near the door is prone to show wear (if not split). This is a known problem until the 2002/3 yr I think, is when they made a change to the design. I use Huskyliners to line up the front and they do a good job at protecting the carpet.
Engine: I use synthetic and try to change it every 5K. This engine maybe prone to sludging - a very heated topic. So every little bit you can do to change the oil more often or with better components, please do. I use either the Toyota filter or Mobil1, nothing else.
Transmission: Drain and fill it, I would recommend it, every 15K. I notice that my RX is smoother shifting after a drain and fill operation. I do not recommend flushing it because I can't be sure how clean their flushing machine is, and that may introduce contaminents into my transmission.
O2 sensor : Your car has 3 of them I think, and any one of them can go bad. Might run you couple hundred to fix. Nothing you can do to really prevent it.
Enjoy your car!