Since it came up last week and we do have a host of new drivers. Remember, if you think you were given a black flag unjustly (we all know the sim isn't perfect, and there are sometimes extenuating circumstances), key up when its safe to do so and request it be cleared. We will talk amongst the organizers and decide whether to clear it.
If we do clear it, we will usually go back and look at it post race. If we cleared a black flag and you did in fact commit the offense you were being flagged for, you will be penalized post race with the severity of the penalty depending on the situation. And be warned, if it is apparent you requested the black flag to be cleared and you have obviously done it to gain an advantage, expect that penalty to be stiff.
Remember, we are racing with you guys. If it is not safe for us to clear you, we might not. To give an example, if I'm racing side by side with someone at a short track, it ain't happening. Be prepared to serve the black flag and just take the poison, even if not right.
If you want more info, refer to section 4, line 10 in the rule book.