As most of us know, many G35's suffer from creaky seats. Infiniti's fix is to replace the seat frame, but for some us that doesn't work and for those that are outside the bumper to bumper warranty, you're out of luck. My seat frame has been replaced once for rocking, but shortly after, the seat began to creak occasionally. After a year of experimenting with lubricating various points and trying to figure out the location of the creak (which came and went annoyingly), I think I finally found the culprit. The creak on my seat was coming from the left rear (nearest the door) seat support pivot point. The fix involves simply adjusting seat support via the two securing nuts and cross brace bolt.
The potential fix:
Trim piece removal
1) remove the two screws from the front of the seat trim piece
2) remove the plastic clip (black) from the lower rear of the seat trim piece
3) remove seat trim piece by pulling it towards you and then back and up. There is a metal piece that fits into a slot in the seat trim piece which necessitates the need to rotate the piece backwardsa bit.
4) remove seat control units from the trim piece by simply unclipping them
5) take a 12mm socket or 12mm wrench and loosen (no need to remove) the bolt securing the cross brace to the left rear seat support.
6) take a 12mm socket or 12mm wrench and loosen (no need to remove) the nut securing the front left rear seat support to the seat frame.
7) take a 14mm socket or 14mm wrench and loosen the nut securing the back left rear seat support to the seat frame.
8) push the left rear seat support inwards slightly (maybe 1/8") and then with your hand keeping the support in position, lock down the front and back 12 and 14mm nuts.
Reinstall everything in reverse order and try the seat for creaks. If that didn't the problem entirely, continue to shift the seat support around until the noise dissappears.