Open G tuning is the most popular open tuning and can be achieved by lowering the first string down a tone (2 frets) to D, the fifth string down a tone to G, and the sixth string down a tone to D also.
Once in open G tuning all the chords will have different shapes. Next are some of the popular chords used in open G tuning.
It is also useful to practice the open G tuning Blues scale.