It is usually decided at the meeting who will host the next meeting and when. The US hosted the first one, the next one is scheduled for Japan next summer. It has been one per year. Same with the G-8, which used to be the G-7 until Russia was invited. The countries decide if another nation will be added. There are other meetings, which are more regional, such as ASEAN and OECD. The foreign ministries of each country generally have a whole dedicated under secretariat that handles the meetings, agendas schedules, and preliminary talks, and draft the coordinated message at the end.