One important thing to learn about coding is that if you try to write the entire project first, and then go back and troubleshoot it, you're going to have a bad time.
You should get small portions of the code working first, and gradually build up to the final project. This is where Mike's suggestion of using the Serial communication to debug comes in handy; it allows you to test variable code and verify it's result before trying to pipe those result into more code that could also potentially screw the values up.