Typical BE reverse breakdown voltage is about 6V, while the BC breakdown voltage is much higher. Based on this, you can do one of these:
- measure each junction resistance reverse polarized. Depending on the DMM you have, you might be able to see the difference between BE and BC by measuring the resistance of each junction when reverse polarized, the BE has a smaller resistance than the BC when reverse polarized, but this might not work.
- measure the reverse voltage drop on each junction. Put in series a 20-30V power supply, a 100 k\$\Omega\$ resistor, and the junction of the transistor as a diode reverse polarized. Measure the voltage drop on the transistor junction while reverse polarized. The reverse voltage on the BE should be much lower than the reverse voltage on BC.
- same as above, but use the internal voltmeter's resistance instead of the 100k limiting resistor. Put the voltmeter in series with the reverse polarized junction and the source. BE will only "take away" about 6V out of the total voltage, the rest will be to be seen on the voltmeter, while the CE will "take away" most of the volts so the DMM will should display close to nothing (or less volts anyways than when doing the same with the BE).