In many situations the standard fingering for a chord can be altered to make a specific chord progression easier to play. Consider Turnaround No.1 in the key of G:
If the Em chord is played with the first and second fingers (instead of the second and third), then the pivot finger principle can be applied as such:
G to Em: First finger acts as a pivot, remaining on the fifth string at the second fret.
Em to C: Second finger acts as a pivot, remaining on the fourth string at the second fret.
This will make these chord changes easier and smoother.
You must select alternative chord fingerings carefully. In most cases the conventional fingering will be best; any other fingerings used will be determined by either the preceding or following chords.
G7
When playing the G7 chord make sure that the first string sounds clear.
C7
The C7 chord can be formed from a C chord by adding the fourth finger.