Identify the key
Identify the scale
Find the chord tones of the melody note
Use diatonic chords from the key
Choose chords that support the melody
Add thirds above the melody
Add sixths below the melody
Keep voices in smooth motion
Avoid parallel fifths and octaves
Use common tones when possible
Resolve dissonance to consonance
Match chord changes to strong beats
Use passing chords sparingly
Test the harmony by singing or playing it
Adjust until the progression sounds balanced