I find that the most comfortable way to play the G major chord is with middle ring and pinky fingers. The reasoning is that you hit the second fret with your middle finger which leaves your index free when you transition to or from another chord that has a fingering on the first fret like an A minor or a C major. If you use your index for the second fret you'll have to slide your hand up one fret which requires more time and dexterity.

Just focus on the low E and A strings first and ignore your high E. Find all the angles of fretting it where both strings ring out and then find the range where you feel the most comfortable then its just a matter of practicing to get muscle memory so that your fingers will automatically go to that position when you want to play G major.