What are the three questions that you can ask that will identify hidden assumptions?

The premise that supports a theory or argument without that assumption being made explicit and the holder of the they may often be unaware of it is called hidden assumption. There are two steps involved in identifying hidden assumptions. First find out whether the argument is valid or not, if the argument is valid then there is no hidden assumption.

While if the argument is not valid then you should check what additional premises need to be added to argument to make it valid. These additional assumptions are hidden assumptions.  

One can also ask what the assumptions mean and why would be person accept such assumptions and should I accept the assumptions of the proponent to find out about the hidden assumptions.

answer; software failure, and human error;