Fleming’s Left Hand Rule allows the direction to be predicted of the force on a current carrying conductor, placed at right angles to a magnetic field.
The first finger, second finger and thumb are first placed at right angles to each other. The first finger points from North to South in the direction of the lines of flux of the magnetic field, while the second finger points in the direction of conventional current flow. The thumb then indicates the direction of the force acting on the conductor.
Notice the underlined letters in the illustration which suggest one way to remember the purpose of each digit. Also, use of the left hand rule for motors (and right hand rule for generators) may be remembered as ‘motors drive on the left’ – if you live in the United Kingdom at least!