Evidence-based studies indicate that longevity is based on two major factors, genetics and lifestyle choices.
Twin studies have estimated that approximately 20-30% of an individual's lifespan is related to genetics, the rest is due to individual behaviors and environmental factors which can be modified.
Don't smoke, don't binge drink, eat a healthy diet and take regular exercise. This can add 10 years to your life.
Maintain and develop strong social networks, with family or friends. Some studies suggest this has a protective effect on health.
Take advantage of any educational opportunities available in your adult life, even if you didn't do well at school. This seems to have health benefits.
Volunteer - There are likely to be opportunities to volunteer wherever you live and some studies suggest this can help maintain mental health and improve life expectancy.