Perhaps someone is trying to convince you to switch to free range eggs. These eggs cost more, but they mean less suffering by chickens. This sounds reasonable, you can afford to spend the extra money, so you resolve to buy free range eggs when available.

Say someone else wants you to switch to wind power. Your electric bill will go up by 60%, but you won't be contributing to climate change with your home electric use. An additional 5 cents per kWh isn't so much, so you decide to do this too.

Another tells you that most chocolate is produced by slaves, and so you should switch to slave-free chocolate, which means organic or fair-trade. It costs three times more, but chocolate isn't a large part of your budget and you can spare the money.

You're now spending some money on virtuous eggs, other money on virtuous electricity, and a bit more money on virtuous chocolate. Each of these is good, but could you do better? Your consumption choices motivated by a desire to improve the world should compete with charities for the place of 'most effective', and whichever wins should get your money. When someone suggests you spend money on a more virtuous version of something, ask whether it is the most good you can do for your dollar.