I like how the answers to your very legitimate question are either:

1) make a decision as a leader of a country / major player in the global economy

2) do small stuff that are very hard to quantify in effectiveness (eg call legislative representative, or go vegan)

3) dramatically change lifestyle

I fail to see how any of those are realistic. Especially 3 has never been shown to be implemented willingly by people, given that if not coordinated, will result in social isolation.