How to Measure low resistance accurately talked through in this white paper from Bourns. Link here (PDF)

Resistance value measurement tests typically use standard multimeters with two measuring wires. This measurement method is suitable for resistance values higher than 10 ohms, but is more prone to inaccurate results when measuring lower resistance values. This is especially true of current sense resistors with resistance values under 100 milliohms. Measuring resistance values less than 1 ohm requires the tester to apply a four-wire (Kelvin) measurement method.