5.32Dominant preparation

Try:

C → G7 → C

Simple.

Now:

C → Dm → G7 → C

More satisfying.

Now:

C → Am → Dm → G7 → C

Longer again.

Each added chord creates a longer path toward the destination.

You can think backward:

Want to arrive at C?

Use G7 before it.

Want something before G7?

Use Dm.

Want something before Dm?

Am often works.

So:

Am → Dm → G7 → C

This backward-thinking method is extremely useful when creating harmony.