As a Research Fellow at Cambridge University, William MacAskill spent five years developing the philosophy of effective altruism, which applies data and scientific reasoning to the normally sentimental world of doing good. During the course of his research he concluded that many ways of making a difference achieve little, but by targeting our efforts on the most effective causes, we each have an enormous power to make the world a better place.
In his book Doing Good Better he introduces the principles underlying effective altruism and sets out a practical guide to increasing your impact through your charity, volunteering, purchases and choice of cause.