Minor triads are derived from the minor scale, and are the basis of the minor chord.
They differ from the major triad in that they have a MINOR THIRD instead of a major third, which basically means we flatten the third note (move it down one semitone or one fret). Let's look at the natural minor scale, in the key of A:
To form a minor triad, we again take the 1st (A), 3rd (C) and 5th (E) notes and play them together. The 3rd note is flattened when compared with the major triad, all other notes stay the same. So, the fingering will be:
For example if you wanted to know C minor, you would find that it contains the notes C (1st), Eb(b3rd) and G (5th) from the C major scale.
For D minor you would use the notes D (1st), F (b3rd) and A (5th).
For E minor you would use the notes E (1st), G (b3rd) and B (5th).
For F minor you would use the notes F (1st), Ab (b3rd) and C (5th).
For G minor you would use the notes G (1st), Bb (b3rd) and D (5th).
For B minor you would use the notes B (1st), D (b3rd) and F#(5th).
The following diagram shows the difference between a C major and C minor triad. You will see there is only one note different - the third note is flattened (moved down one fret).