One of the best writing book that I come across. She has given many tips on how to start writing.
I read and applied one of her methods on writing that is: Write non-stop for 5 minute, 10 minutes (you decide) anything that comes to your mind, without stopping, without punctuation and do it as fast as possible. Do this everyday to make it a habit. You can prepare a list for this writing exercise. The more you practice, the easier it will get.
There are lots more practices or "To Do" in her book. It is a good "How to" book that helps you with writing.
So, Just Write!