It’s impossible to prove you are not dreaming. So actually the trick is to always be aware of the fact that you are dreaming.
If RC’s don’t work, you still could be dreaming
but if RC’s work you are definatlly dreaming
Telling this, because you don’t want to think to quick, eh I’m not dreaming on moments that you are 
Just wondering about it in your mind throughout the day will already help questioning your reality in your dreams