Worlds 33, 57, 120, and 136 are the free to play legacy-only worlds, worlds 18, 97, 115, and 137 are members' only legacy worlds, and world 66 and 135 are EOC-only worlds. In those worlds, you are automatically switched to the configuring mode and need to hop to switch it off.
RuneScape players can switch between modes anywhere in the game, unless they are engaged in combat. To properly switch, the RuneScape player should be not in the middle of something, or be able to take a brief break. It generally takes less than five seconds to toggle between EOC and legacy mode, assuming the RuneScape player knows which buttons to push.
The following slideshow list will detail the process of toggling between EOC and legacy mode in RuneScape.
Toggling from Legacy to EOC David Farrell, RuneScape game client
Toggling from Legacy to EOC
Toggle from Legacy to EOC. Look for the settings tab below the inventory. It is the one with the hammer and wrench. Click on that to open the game settings menu.