Lots of things to keep her good but Oil and coolant are the key! My JTD W plates oil is changed every 6000 miles, air filter every May (before pollen kicks up), coolant every year in October (before winter). Some may say its too frequent but shes done nearly 90,000 and has just passed her MOT today with one advisory for a windscreen chip which is going to be repaired. Photos in my Gallery.
Other regular checks on brakes, battery and body work condition.
Find yourself a well recommended garage (not the cheapest!!!) and have it fault code read when you get it just in case.
Keep the road salt off as best you can with regular rinsing and quality polish. Two I use are Halfords own in the blue container, its cheap but works really well and Autoglym for the show quality finish.
Interior polish is dependant on whether you like shiny, smelly or just good and clean. For shiny, Flash Dash is superb and in a range of smells. For clean plain old Mr. Sheen or Pledge! Either of which will clean the windows brilliantly.
Micro fibre cloths in all polishing and super soft brush or sponge for exterior cleaning.
Lots of members will have their own choices but these work for me on the car and the Lorry.