I wrote an article for Acoustic Guitar Magazine about chords and how to improve your knowledge of chords back in the 90's - back in the day when a magazine was something you actually held in your hand :)  I wrote one for them again just this year on a similar topic with a fancier title - "Expanding Your Harmonic Palette" - and included a video explaining the article and demonstrating its finer points. If your a guitarist and you watch the video I hope it helps you improve and that you enjoy it. It could also be considered a free trial first lesson, because the information here is terrific, but it's only the beginning. Click Here To Watch The Video