Examples of chords for a banjo tuned in G include C minor, D minor and E. BanjoChords.net offers a free chart of chords for banjos tuned in G, as of 2015.
To play the C minor chord, a player places the first finger on the top string, first fret, and then the player places fingers two and three on the bottom two strings, first fret.
For D minor, a player places fingers two and three on the bottom two strings, third fret, and the first finger goes on the third string, second fret.
A player plays E is with the first finger on the second string, first fret. Finger two is on the top string, second fret, and finger three is on the bottom string, second fret.