This is how I do it, First remove all door panels and rear panels so u can visually see the speakers,then remove head unit to get at stock wiring harness,next get urself a 9 volt battery and some speaker wire or duct tape and connect wire paying attention to +,- to 9 volt then take wire and touch to ends of stock speaker wires paying close attention to cone movement ,when cone moves out its pos ,in its -,not only will this help determine polarity but also location of speaker fl,lr and so on.Also if u have a car that they make a harness adapter for I'd go that route, And don't forget to disconnect - terminal of car battery!!!or its fuse blow city!//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif