Look dear, it is what others believe to be in BIG 4, u should have reference. I Don't believe so dear. To be there u need to get first prepared your self for the BIG 4 i.e. interviews, personality development, speaking skills and other skills such as your behaviour, common sense, management of people, ideas, you should have the leadership skills etc. There are many more things to be there.
One more thing i would like to say that just prepare for 100% and u should know better know what is 100%, if you are not selected there than there should be some reason for that but dont let your self down due to any reason.
I have met with most of the people asking for the same questions many of them fail and pass also. But i only told them just give your 100 % and wait for the best..there will be your time one day.
Therefore i believe that
TOUGH TIMES NEVER LAST BUT TOUGH PEOPLE REALLY DO.
So take charge and good luck.
Regards