Galley 1 (G1) will be most FWD. On single aisle aircraft the length of 737/320 Galley 4 (G4) will be most aft, with G2 and G3 in between (if fitted).
On longer aircraft such as 757/767 the G1 will still be most forward but the Most Aft Galley position is G6, with a combination of G2-G5 dependant on cabin configurations.
Sometimes you would see A or B or LH/RH as identifiers for where the galley is fitted. I.E G1B