Communicating the Message

One of the greatest problems with creating a film is when you have to work with others. Everyone has their own experiences and when you write the script you are basing the action on your own experience.
When you say "walk through the door", you have an action visualized in your head. Its more than just walking thought the door, you have a speed, body position, body language, style of entry, etc. All of these are being pictured in your mind. But when someone else reads "walk through the door", they visualize what you are saying differently. They are forming a similar but different way of doing the action. No two people will ever visualize a written action the exact same way, especially if the writing is not very descriptive.
This is why you need to be very descriptive when you write your script. You need to describe how you want that person to do the action. There is a big difference between "walk though the door" and "walk timidly through the door, scraping along the door frame, clutching her books to her chest and holding her head down as if afraid to make eye contact with anyone in the room." or "marched brazenly into the room, chest out, eyes bright searching for a competitor to test his competitiveness against, swinging his arms at his sides as if he was on the parade ground." These are two extremely different images and yet they both mean "walk through the door".
Even when you are being more descriptive there will still be differences in the way the writer, the director, and the actor visualize the action, but now they are small differences which are easier to work out while filming. A good writer will include enough information to give the desired action but leave some interpretation so others can make the action their own.

What problems have you had writing your scripts?