I tried searching for trunk leaks but I think the leak I have is not that common. I am getting water dripping down from the rear tray/hinge into the trunk. Where is this coming from? Do I need the rear window pulled and reinstalled to fix this?
If you haven't, start by crawling in the trunk with a bright light and inspecting the package tray sheet metal for rust or holes.
It takes two people, but go in the trunk with a light, shut the lid (suggest not doing this with someone who doesn't like you...), have the outside assistant run water on different areas around the window. Not a spray, but a smallish stream from a G/H so they can control where it goes, this might help you locate the source.
There are also two black plastic "vents" on the sides behind the rear bumper. I have found that those tend to pop loose and leak around the seal or the foam seal becomes worn. If the seal is worn, I just put some caulk on it and snap it back into place.
Check the gaskets on the tail-lights, they tend to be worn out, if the tail-lights themselves aren't fully screwed down (there's three nuts in the on each tail light) they will let water seep inside..
Gaskets around the lights are already sealed up and I don't think it is the flaps for the vents it is coming from above. I will try and check the seam above the hinge and maybe try the water trick.
Quarter panel is welded on rather than bolted and anywhere the metal is joined has to be waterproofed. Look close at your caulking there, any cracking in it needs to most likely be recoated with something to waterproof it.