In your first public speech as President, apologize to each country by name in whose affairs the U.S. has meddled from the very birth of American foreign policy to the present. Pay restitution if necessary.
Adopt a strict “defensive only” military doctrine while publicly denouncing past preemptive and offensive military action. Invest heavily in diplomacy.
Commit 75% of your annual $441 billion military budget to global humanitarian aide. Start at home by ensuring that everyone has an opportunity to be educated, has access to health care and the basics for a dignified life.
As a part of the humanitarian push rename the “War on Terror” to the “Global war on disease and poverty” in recognition of the fact that that’s the only way you’ll really stop global terrorism.
Set an example for others to follow:
Listen to the people, all the people, around the world.
Be honest and transparent, admitting to mistakes and bad decisions rather than sticking to them to the death.
Instate a zero tolerance policy on corruption in government and enforce it unrelentingly. Even if it means firing friends. Even if it potentially means your own resignation.
Be open to compromise, even if the opposing view goes completely against your own. Remember you’re governing a vast number of people not even two of whom will see eye to eye on everything.