Another technique involves inserting dominant chords before other chords to create a stronger sense of movement to the next chord. The root of a secondary dominant is going to be a perfect 5th away from the chord that the secondary dominant is going to lead to. (i.e the V of ii is going to be a perfect 5th away from the ii chord.) Here is an example with the harmonized C major scale with some secondary dominants added.
Secondary dominants can precede any chord but usually not in front of diminished chords. You can use them in front of both major and minor chords.
Coming up next, we will be looking at the use of diminished chords.