How to Trap a Leprechaun:
Promise them food.
Set the elaborate trap, using things usually found within the room the trap is to be set.
Realize said Leprechaun's will be a bit ticked off by the fact that there is no food, so one must put out gold. For this trap we used some pirates booty gold from my treasure chest,
By the time they realize the gold is fake, they should be caught.