On my 325i the idle control valve is located on a pipe comming off the air intake. If you follow the air intake pipe from the air filter box, you will find a small pipe comminig off before you get to the throttle body. The small pipe goes into a metal 'tube', and then I think the pipe out of the other end goes back into the main engine air-intake bu the other side of the throttle neck. You will see an electrical conector atatched to the side of it as well. My car is a UK spec 325, not sure if that makes a diffrence.
I have been told you can clean them up with brake cleaning fluid. I just got a new one from the scrap yard, then found it was the a split in the airintake pipe.
When the engine is running the idle speed should increase if you remove the electrical contacts, and the resistance should be 9 - 10 ohms at about 73 degrees F, (23 degrees C)
Hope that helps