Thanks to: Ron Knight and Ian T.  Brickbats: Me! 

  Umpires are taught to ask the following 4 questions in order:
  1) P - Where did the ball Pitch? (if outside legstump means not out)
  2) I - What did it Impact? (must not be bat or hand holding bat)
  3) P - Where's the Point of Impact? (See explaination below)
  4) S - Would it have hit the Stumps? 

  The 4 questions to be asked are remembered by 
  noting the following mnemonic - PIPS.