One of the requirements to advance beyond First Class requires serving in a position of responsibility or leadership.  The times are listed below:

First class to STAR Star to LIFE Life to EAGLE 
Four (4) months Six (6) months Six (6) months

Serve actively in your troop in one or more of the following positions of responsibility (or carry out a Scoutmaster-approved leadership project to help the troop): Patrol leader, Assistant Senior Patrol Leader, Senior Patrol Leader, Troop Guide, Order of the Arrow troop representative, Den Chief, Scribe, Librarian, Historian, Quartermaster, Bugler, Junior Assistant Scoutmaster, Chaplain Aide, Instructor, Webmaster, or Outdoor Ethics Guide. The Positions of Responsibility tracking matrix is accessible here.
To get rank info, go to
Advancement process document
Scoutmaster conference and Board of Review Schedule