The wargame company SPW has the Der Weltkrieg Series board wargaming WWI see www.spwgame.com
which lists the games and has an step by step video on how to play it. The introductory game is tannenberg. There is also The Eastern Front 1914-1917 6 separate games Tannenberg, Galicia , Serbia, Rumania, GorliceTarnow,and the Brussilov Offensive as well as East front campaign game. For those of us who want to refight WW I in the East.