Here are a few examples:

If we are dealt 3S, 5S, 3D, 4C, 9H:

Place 3S down first (to indicate that the secret card is a spade),
then 3D, 9H, 4C (low, high, middle)
to indicate that the secret card is 2 more than the 3S, i.e. the 5S.

If we are dealt 3S, 9S, 3D, 4C, 9H:

Place 3S down first (to indicate that the secret card is a spade),
then 9H, 4C, 3D (high, middle, low)
to indicate that the secret card is 6 more than the 3S, i.e. the 9S.

If we are dealt 3S, 10S, 3D, 4C, 9H:

Place 10S down first (to indicate that the secret card is a spade),
then 9H, 4C, 3D (high, middle, low)
to indicate that the secret card is 6 more than the 10S, i.e. the 3S.

If we are dealt 2H, JH, 4D, 4C, 4S:

Place JH down first (to indicate that the secret card is a heart),
then 4D, 4S, 4C (middle, high, low)
to indicate that the secret card is 4 more than the JH, i.e.the 2H.