What's the best way to find an oil leak?

My friend's 1999 Beetle has an oil leak.What's the best way to find an oil leak?
Pressure wash the under side of the engine. Then the new oil leaking will make the leak easier to spot.What's the best way to find an oil leak?
look under the car and see if it is leaking? check is the oil stick and see how low it is
If you just can't ID it from looking around under the area of the leak (yes, sometimes the oil runs sideways, making that tough), there are fluorescent dyes that can be added to the oil. If you get on it right away with a black light, the source of the leak will be immediately evident.
There is a dye you can get to put in the oil. Go to a parts store like Advance or Auto Zone
Thoroughly pressure wash the engine(protect electronic components by bagging and taping). Let dry. Start the car and let idle for a few minutes. Inspect closely for signs of leakage. If none found drive a short distance and check again.
Take to dealer.