"We are social animals and it is in our own interest, if we want to live a happy life, to think of the rest of humanity." - Dalai Lama
While we might forget it, human beings are animals. We have packs (families, clans, groups of friends) we have hierarchy, and we have a few things we need to survive. The way that we live now, however, makes it easier and easier to forget that we are interdependent beings and that what is good for one of us should also be good for the entire "pack."
Next time you make an decision, think about how it could affect others and if there is a way you could change your decision to work in a way that improves someone else's situation as well.
Once you start considering others before yourself, it becomes a habit, so start today.