Watch the Diatonic Progressions in D online guitar lesson by Brad Carlton from Guitar Lab: Solid Strumming
This lesson will take you through 30 different progressions which involve two different diatonic triads. They are grouped into six categories each of which use one of the diatonic triads as home base. By practicing these 30 progressions you will develop your facility at changing chords and in addition you will train your ear to hear these different harmonies.
After you practice these 30 progressions, you should then mix and match these chords and use your ear to create your own progressions. I will demonstrate in the video how you can use this concept to develop sections of songs.