How do I check a BJT transistor if it is still functional?
You can do a simple check with any multimeter that has an ohmmeter function.  Use the multimeter on a low ohms scale.

Check the resistance between the base and emitter with the red lead on the base and the black lead on the emitter, then repeat with the red and black leads reversed. If the transistor is good, you should get a low reading and a high reading. Repeat this process with the base and collector.  You should also get a low and a high reading.

What you are doing is checking the diode junctions; in one reading, the junction is forward biased by the battery in the multimeter and will yield a low resistance, in the second reading, the junction is reverse biased and will yield a high reading.

Also measure the resistance between the collector and emitter and then reverse the multimeter leads as before. In this case, you should get a high reading in both measurements since you are measuring across back to back junctions.  If all of the measurements are OK, then the transistor is probably good,  If any of them are not, then the transistor its probably bad. 

By the way, multimeters vary as to the polarity of the battery during resistance measurements.  In most, the positive terminal is connected to the positive battery terminal but some multimeters have this reversed.