this process is not an easy one. there r 2 ways u can do it and neither one is too easy.
first of all, if u have a center console, then this will b the best and easiest of the two. first u wanna take out ur deck and totaly disconnect it and set it somewhere out of the way. now u will need to take the console out, u should find some cut outs in the carpet. now i dont know what kind of car u have so this could be harder than it sounds!
through the area where the deck goes, u will need to find, with ur hand, from the top or bottom, an opening for the RCA's to go through. once u find this, run the RCA's through there and under where th console goes. u may have to find the top of the carpet at the fire wall and run through there. if so get a metal coat hanger and run it under the carpet from one of those cut outs under the console. pull them through till the end thats gonna connect to the deck is out just far enough to hook them up to the deck.
now u have to take the sitting part of ur back seat out. use the hanger again and pull remaining slack out. now u can either go into the trunk and use the hanger again and try to find a gap big enough to fit the cables through or pull the back part of the seat out. i would pull the seat completely out. if u pull it out, good. now just find the lowest point in the center of the frame work in the trunk, and poke a hole through and run the cables through. in this whole process make sure the cables never come in contact with sharp metal edges. this way also takes the least amount or lenght to get to the trunk.
the other way involves finding a path through the deck location, to under ur dash. u will need to run the cables across under ur dash and wire tie them to several places. now u need to take out the trim pieces. take out the one u step on out first. if it is 4-door then u have 2 of them. now u will need to take the kick panel out, the piece of trim to the left of the brake peddle. now completely take the back seat out. now the trim that the seatbelt is attached to. if its 4 door then u may have to remove the rear quarter panel trim also. now its the same as explained above in the first example.
just e-mail me with any questions u may have.
20 yrs personal exp.