One player has the rail tiles and the other has the road tiles. They alternate turns placing one of their tiles on the board. Each tile shows a section of road or rail with up to six connections.
When placing a tile, the only rule is that it must connect with a tile already in play (apart from the first turn). It doesn't matter if it connects to a road or a rail but it DOES NOW matter if other connections lead to dead ends. ALL connections must connect to other connections or the edge of the board.