A transistor can be considered as two back to back diodes for test purposes as in the top of the rather haasty sketch.
So if you set a multimeter on the ohmsx100 range and watch the meter (either digital or analog, but analog is best) and apply the leads to the collector base diode one way and then reverse the leads you will get readings as shown.
Note I have shown an NPN transistor, a PNP one will work the same with the red and black reversed.
Then you can do the same with the base emitter diode and finally with the collector emitter pair.
You should check a known good transistor first to see what happens.