Folow the Service Schedule in the handbook, typically a big service once a year, with oil & filter change 6 monthly. There are some important jobs that occur say every 3 years (eg brake fluid change), or every 50,000 miles (eg cam belt) which is why you need to follow the manufacturers schedule. After over 35 years of motoring I have realised that regular servicing is the absolute key to reliability and long service. I get trouble free motoring for well over 100,000 miles in all my cars by reasonable driving and regular services. Many people do much of this work themselves with the help of a Haynes manual or similar, leaving the hard stuff to a good mechanic.