Start by playing the C major scale: C, D, E, F, G, A, B, C. It is the only scale that requires no accidentals (sharps and flats). On the keyboard, C corresponds to the white key immediately to the left of two black keys.
Play the G scale: G, A, B, C, D, E, F# (F sharp), G. Find the G key by looking for three black keys and playing the white key to the right of the first one.
Play the F scale: F, G, A, Bb (B minor), C, D, E, F. The F key is to the left of the G key.
Notice the scale progression. In all major scales, half-steps occur after the third and seventh notes in the scale. Generally, half-steps move between white and black keys. E/F and B/C are the only half-step intervals between two white keys.
Begin learning the three types of minor scales: natural minor, harmonic minor and melodic minor. Play a natural minor scale by lowering the 3rd, 6th and 7th intervals of a major scale by a half-step.
Play a melodic minor scale by lowering the 3rd interval when ascending. Play the natural minor scale when descending, lowering the 3rd, 6th and 7th.
Play a harmonic minor by lowering the 3rd and 6th intervals. This leaves a step and a half between the 6th and 7th interval.