Marion — listen to Rick. I did the G with the index/5th for years, just because that's what I was shown when I first started playing. Rick made the same suggestion to me and it has worked wonders on what I can do with melody and countermelody. The only exception is one song I do — Keep Your Hands Off My Woman — that requires a fun up on the 3rd, 2nd, 1st strings out of the G position. I find it easier to walk it up with the ring and little fingers, which requires the index to play the 5th string.

Fretting the 4th string (D) at the 3rd fret while playing a normal D configuration gives you an inversion of a D7. If I remember the terminology from theory classes lo so many years ago, if you're still playing the 5th string (A) as well, that would be a second inversion, since your bass note would be the 5th of the chord. If you're playing the third of the chord as the bass note, it's a first inversion.

If my memory is faulty on that, I hope somebody with a better command of theory than I claim will sort it out for you.

On the E7, both are valid but I often play a combination of the two — it puts a LOT of 7th sound in the chord and all the motion that carries. It also lets me bend (whether the D string has been opened or not) the B string/3rd fret for an even stronger call for resolution to the tonic. Useful in blues.

cheers,

david