How to sell a screenplay?

I am seeking advice. I am a playwright, I have never written for the screen but ... A production of one of my plays is currently windng down here in Adelaide. We have only two more performances to go. One of the most common remarks made by audiences is that the play should be turned into a film script or at the very least that I should attempt to sell it to a film maker. I am a complete babe in the woods in this area, my entire experience of the film industry is watching films and the occasional extras work. I am a theatre person pure and simple. (Well maybe not so pure.) Has anyone got any helpful advice?