I would magically make everyone feel loved, wanted, and appreciated. I've found that no matter what ails a person, love is usually the medicine.
Its going to take a lot more than just one thing.
Get rid of most of the people.
Replace EVERY SINGLE person in ALL forms of the government.
I doubt we could do this world wide but we could do it at home here. Combine the History of Diplomatic Relations of The World's Nations and inter personal diversity awareness together into a basic subject taught in one year long class to all Middle Schools in America. How's about that for a game changer!
Eliminate television. In my opinion it has dumbed down our society, hypnotized us and made us unable or unwilling to find creative ways to spend our time.
All people have plenty of food for the rest of their lives.
Send Justin Bieber on a NASA mission to Mars