The mezuzah should be placed on the right side of the door. The right side is determined by which side is on one’s right when they enter the room, there is no difference between a right or left handed person. When there are two rooms next to each other, for example a living room and a storage room, the right is decided by which direction people usually go from. If it is equal, then it is determined by which room is more of a main room. If they are equally main, then it is determined by where the hinges are and into which room the door opens. If there is no door with hinges, one should put the mezuzah on either  side without reciting a bracha.