The standard alternating bass line for a G chord is between the notes G on the third fret of the sixth string and the open fourth string (a D note).
The melody notes used with the previous bass line are taken from the G Major Scale and the G blues scale.
Example Nine shows a popular way of using the B@ and Bb in the melody. Try not to sustain these two notes together.
Example Ten uses the extra notes on the second string. Pay special attention to the fingering.
Example Eleven combines the G Sixth and the G Seventh chord. Also observe the A note which is used in the last bar.
Example Twelve is similar to Example Eleven but shows how you can use a harmony on the second and third strings.