I was doing some reading, particularly about the 30 year's war, and my textbook mentioned that the Peace of Westphalia was the first time representatives of all sides convened to discuss who got what, the system we use to. How were peace conventions conducted before this?
An other information you'd be willing to share on the 30 year's war and the making of peace treaties is most certainly welcome.
Before the Peace of Westphalia 'international relations' were almost solely bilateral. Even in wars with multiple parties on each side, negotiations were usually bilateral and bilateral peace treaties would be signed (sometimes even to the detriment of supposed allies). So there were no peace conventions before the Peace of Westphalia; it was the first time such an event took place.
That these treaties were bilateral is evident from the way oaths to uphold the treaty were sworn. For instance, the Peace of Cateau-Cambrésis in 1559 (at the end of the Italian Wars) consisted of a treaty between France and Spain and a treaty between France and England. The French King exchanged solemn oaths with Philip II of Spain, with a seperate exchange of oaths taking place between the French King and Elizabeth I of England.
Source (for the last paragraph):
M.S. Anderson, The Rise of Modern Diplomacy 1450-1919, London 1993 (p. 15-16).