If I were US President Woodrow Wilson and other representatives of the Allied and Central powers, I would want to ensure that there would be a set area of rules that define how warfare goes. I would ban certain weapon uses for war if they are too cruel. In an effort to retain relations, I would also not want to administer punishment to the "losers" of the war as it would increase hostility and rebellion. This would be a hard one, as France and Britain are trying to administer revenge against Germany and Austria-Hungary. I would also want to ensure that international affairs were not gatekept between certain nations, especially if it had to do with the expense of another nation. World leaders should meet at a regular basis in order to understand each other's aims and goals, along with resolving conflicts if necessary.
All of these points were addressed by President Wilson, and most of the agreements drawn up in the Treaty of Versailles are still in effect or have decedents of them. Hope this helps!