Every fingering that fits a hand
300001
open
300201
open
303003
open · no 5
30300x
open · no 5
300401
easy
What is true of it
G9 is G, B, D, F and A — 1, 3, 5, b7 and 9 counted from G.
On an instrument that cannot reach all 5, the 5 and 1 go first, in that order.
The easiest of the 5 fingerings below is 300001: 2 fingers, held at the 1st fret.
4 of them use open strings, which is what makes a shape quiet to change to.
Where its notes are on the neck
The brass dots are G, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
G9/B
x20201
G9/D
xx0201
G9/F
100001
An inversion is the same chord with a different note lowest. The name changes to a slash name because the bass is what a listener hears as the foundation.