For a D chord push your wrist forward and bring your elbow into your body. This is good advice for many chords and it often helps you make the chords ring out clearer.

Keep all your finger joints locked up. The video explains more.

Always check your new chords by picking them.

HOMEWORK: Play and change between A, E and D chords. Use the 60 second chord changing technique with all 3 chords. The video explains how to change between these chords effectively.