When rewiring your tail lights and how do you know what wires go to what

Use a TEST LIGHT - turn on left or right signal - use test light to find that particular wire - same with the other lights. When connecting wiring to tail light itself - bulb will be a lot brighter for the signal lights .. Dimmer for parking lights. Once signal lights are connected - so will be the brake lights - it's the same wire! IF you can't figure it out using this procedure - recommend seeking *hands-on* assistance from auto repair savvy personnel.