Uhm... that's not smth very hard to do once we get to know about how important simple acts and habits are.
The most important thing I'd change the world is the way we treat and see Education. In my country, good education = paid education. That's not good at all cause the students who study in public schools don't give value to it anymore, they destroy it, don't respect the teachers etc.
I think that if Education changes, everything changes as a consequence: Security, better pattern of life to citizens, a society worried about its problems and WORLD'S problems too.
In my opinion, Education is the beggining of a better world.