By the slope of the graph between Potential difference and current flowing through the conductor.
Usually the experiment to find the resistance of the conductor involves a simple DC circuit with a battery, the conductor in the form of a wire. Perhaps there are more conductors (known resistances) in the circuit.
The values of voltage in volts applied between both ends of the conductor and the resulting current value in Amperes are both recorded. They are plotted on a graph. like: (V1, I1), (V2, I2), (V3, I3)....
The resistance can be taken as the average of (V2 - V1) /(I2 - I1) and (V3- V2)/ (I3 - I2) , and so on..