3. Go Easy On The Symbolism
There's nothing wrong with imbuing your screenplay with symbolism - many of the greatest screenplays of all time are built around subtext and symbolism. Thing is, though, the symbolism inherent in these screenplays is subtle and carefully weighed. Prometheus is a movie constructed out of the most ham-fisted movie symbolism I've seen in a long time: worst of all, it doesn't make much sense, as if it's stretching to be complex for the sake of it, despite the fact that the movie doesn't even have a properly developed storyline. So what, you say? Isn't it better to have some degree of symbolism, anyway? I'd argue not: it doesn't work because doesn't have a plot to attach itself to: good movies work as symbolism, because the symbolism is derived from the plot - how can Prometheus hope to have symbolism when the symbolism doesn't have anything firm to cling to? Instead, it becomes a movie that is relentlessly trying to have "ideas" larded into it. The key to layering your own screenplay with symbolism? Just write it. If you've got a good story, the symbolism will fall into place by itself. You shouldn't be trying too hard to make your script more intelligent than it actually is: that will come through in your writing anyway. The point is, symbolism shouldn't be at the forefront of your script. Prometheus makes this mistake over and over again: jamming it in our faces is just obnoxious, especially when its "big ideas" are just a means of distracting from a lack of plot.