A minor scale (its full denomination should be natural minor scale) is a scale is which we have semitones between intervals 2 and 3, and between intervals 5 and 6. The other intervals are a full tone. Following the rule that we apply to the major scales, with whole and half, the minor scale should be w-h-w-w-h-w-w.
Let’s take an example. We are going to write the A natural minor scale. We put the 7 notes beginning with A, and we correct interval distances when needed, using sharp notes.
A B C D E F G
That was pretty easy, right? As a matter of fact, we didn’t have to alter any note. Does it remind you of something? That’s right, the C major scale doesn’t have any alteration either. This is because these two scales, C major and A minor, are actually the same thing seen through a different prism.
Let’s have another example, the E minor scale.
E F♯ G A B C D
So, all natural minor scales are built in the same way, they don’t have any secret. Same as for major scales, if you grab a pen and a piece of paper and build the natural minor scales of the 12 key signatures, you will come up with different sequences of notes for each one.