Nationally, it is part of the Extension Service of the U.S. Department of Agriculture. This depends on the group and what it wants to do. Sometimes members have to be enrolled in a project by a certain time to be eligible for a specific activity.
Any place is acceptable if it is large enough and is convenient for the members of the group.
Some clubs meet in leaders or members homes. These teens assist the club leader and members with project work, club programs and activities, and county events. Your main help would be the county UW-Extension office. The 4-H youth development agent will discuss with you your interest in working with youth, your previous experience, and the resources available to you. All volunteers complete application and enrollment forms and participate in an orientation.