The directors pretty much go through the scene as far as what positions they want and where the pop will be. A few directors might try to throw some extra's in for free. But not sure if they would go to the extreme of double vags or anals. And then the talent will more than likely go through there do's and don'ts with eachother (slapping and spitting and such). Also the camera guy might go through what he is looking for as well, look at the camera or don't look at the camera depending on what is being shot. Also how he wants the positions to look. It is pretty straight forward but there is always snags.