When I play chords on the banjo, I actually pick with three fingers. Why? Because a chord, by definition, has three or more notes. For the chords shown below, my thumb plucks strings 5, 4, and 3. My index plays only string 2. My middle picks string 1.
With that in mind, here are some common chords and useful 3F picking patterns to try out in G tuning. Click on the tab to download it as a PDF.