Oh boy 12 cables.. I know how to to do it, have the tools needed, but it takes a long time to type it out.
Basically there are two ways, the short way is....
Put a resistor (or a short) on the far end of a cable.. Search for it with an ohmmeter.. When you find it, label that lead, move the short or resistor to another cable.
Option 2 is to use 100 ohm, 200 ohm, 300 ohm 400 ohm up to 1200 ohm and then measure the resistance, 105 ohms is, of course the 100 ohm, label it and go on to the next.
Have used both methods in the past.