Standard diplomacy involves government-to-government communication; modern diplomacy has begun to emphasize public diplomacy as well.
The United Nations is the most important and influential international, intergovernmental organization.
The international monetary structure involves international institutions, regional trading blocs, private players, and national governments.
A collective military force (when multiple countries pool their militaries) involves both collective security and collective defense.
States can give economic aid to help another country, or implement economic sanctions to try and force another country to change policies.
Arbitration is a form of dispute resolution that can be used to resolve international commercial, investment, and interstate conflicts.