4. Hang out with good people

Seeing others behave dishonestly makes you more likely to be dishonest.

Seeing people behave altruistically makes you more likely to be altruistic:

…these results provide evidence that witnessing another person's altruistic behavior elicits elevation, a discrete emotion that, in turn, leads to tangible increases in altruism. [Psychological Science]

Research shows you become like the people you surround yourself with, so spend more time withthe type of people you want to be.

From Charles Duhigg's excellent book The Power of Habit: Why We Do What We Do in Life and Business:

In a 1994 Harvard study that examined people who had radically changed their lives, for instance, researchers found that some people had remade their habits after a personal tragedy, such as a divorce or a life-threatening illness…Just as frequently, however, there was no tragedy that preceded people's transformations. Rather, they changed because they were embedded in social groups that made change easier… When people join groups where change seems possible, the potential for that change to occur becomes more real.[The Power of Habit: Why We Do What We Do in Life and Business]