How can I make an actor cry? In a film I am making I need and actor to start crying, but I cant think of how I am going to do that without actually making them sad. 

One thing I have heard is that there are eye drops you can get. 

Are there any other options?
Eye drops or saline are certainly simple. Alternatives include blowing dry air at the face just before action, or rubbing the eyes. 

Can your actor not use the old tried and tested method of remembering the death of a childhood pet?