My 1994 BMW 740i is leaking oil. What is causing this?

My 1994 BMW 740i is leaking oil. What is causing this?Could you be little more vague? lol

One major leak on the drivers side of the motor could be a very simple fix. Check the oil filter cap sealing ring. If you have not changed it in a while it will produce a massive leak. Change the oil filter and ring and you might kill the leak. If not where is the oil leaking under the engine? Drivers side? Pass side?