Watch the Open G (DGDGBD) online guitar lesson by Vicki Genfan from Open Tuning Handbook: Rhythm
Although this tuning has a D as it's lowest note (6th string), it's actually a G chord. The Hawaiian guitarists, who play in a style called "slack key", call this tuning "taro patch". It's also a great tuning for playing slide guitar with. The diatonic chords that I've listed on the chord chart are beautiful, folky sounding chords. There are two main shapes, one for major and one for minor chords. The tuning also lends itself to easily using bar chords to play a typical I-IV-V blues progression and it's great for slide guitar playing. Overall, it's a tuning that covers a lot of musical ground, giving you many options in terms of styles of music.
I decided not to use the diatonic chords or blues progression in the exercises and have instead drawn from the progression found in the Nirvana song, "Smells Like Teen Spirit". I added to that progression, bringing in two minor chords, the vi and the iv.
In Level 1, we start with a simple finger picking pattern that features the same 3 open strings (3, 1 & 2, in that order) throughout the exercise while the root of the chords is played on the 5th & 2nd strings. In the 2nd Level, we add a simple yet syncopated strumming pattern. Finally, in Level 3, we add more syncopation and body percussion.