Walters,
PNP vs NPN
The way you tell the difference between the two is by the dodes you see in operation WHILE you are measuring.
An ohmmeter actually is a positive DC supply, like a battery. You measure (send current through the device under test) by connectng the leads to the device.
A diode's anode and cathode can be determned by the resistance reading you get when you connect the positive (red) lead to one side and the negative (black) lead to the other. If you get a low R reading, you've forward biased the diode. Hence, you must have the red to the anode. If you get a high R (relative to the leads the other way around), then your positive (red) lead is on the cathode.
(Do bear in mind that the above is correct ONLY if you have the red lead in the positive hole on the meter and the black in the negative.)
Now the same way you measured the diode is the same as you do for the transistor, whether PNP or NPN.
A diode looks like
------ P N -----
A forward biased diode looks like
positive lead ---- P N ------ negative lead
An NPN transistor looks like
----- N --- P ---- N ----
Now, about telling the difference between the collector and emitter. What I would recommend is this:
For a 2n3904, an NPN Bi-Polar Junction Transistor, in a TO-92 package, with the flat part facing you, you have
EBC
Using this transistor (a very common device incidentally), measure it for yourself and see if you can tell the difference between the diodes. (Do it with several 2n3904's so as to compare.)
The 2n3904's complement (opposite, or PNP) is the 2n3906, and it has the same pinout.
Just ask if you need more help. (...assuming I have time)