The signpost maze is a smaller area, but contains a very important part of the game- The Frog's Song of Soul. To open the hidden staircase you'll need to navigate the signs. To finish the maze you'll need the Hookshot, Power Bracelet, and Sword. Once you meet the Frog you'll need to pay him 300 Rupees for a session of music playing. Learn the song and be on your merry way.