Normal mode uses all of the locations listed by the scenario for the number of characters you have. To make the game easier, decrease the number of locations by 1; to make it harder, increase it by 1. This will generally change the number of explorations needed to finish the game by about 4 (for small locations) to about 7 (for large locations). Be careful reducing the number of locations in scenarios that use villains, as doing so may make it too easy to corner the villain. Also, some scenarios depend on certain locations being present, so be careful to avoid breaking the game.