Set your meter to read resistance, and use the lowest setting at that.
Touch one of the ends of the speaker cables (speaker side) with one of the probes from the meter, and then make contact with the opposite end (amp side) of the speaker cable (one at a time, obviously) with the second probe. When the meter needle (or display, if digital) reads "0" then you have isolated a single wire. Mark accordingly.
Touch one of the ends of the speaker cables (speaker side) with one of the probes from the meter, and then make contact with the opposite end (amp side) of the speaker cable (one at a time, obviously) with the second probe. When the meter needle (or display, if digital) reads "0" then you have isolated a single wire. Mark accordingly.