Make your screenplay synopsis simple, straightforward and easy to read. This is probably the most important tip you should keep in mind. Remember that directors are too busy to try and decipher your meaning. They want to find potential scripts that are easy to understand and easy for them to pitch to producers.
Get some critique from peers before sending your screenplay synopsis to directors. If your peers fail to understand your ideas, then you need to find out why and correct the problems before moving forward.
Create action or intrigue with your screenplay synopsis. You want to give the reader just enough information to get them interested, but not so much that they could make the film without ever seeing the actual script.
Remember that your synopsis is the way you sell your idea. All great ideas need to be packaged with a minimum of fuss and a high degree of specificity. For example, take the guess work out of it for your reader by indicating whether your synopsis is an original dramatic idea, an adaptation or a true story.
Find examples of winning synopses online and use these as your guide. (See resource list below for places on the web to find examples.)