From Mind to Paper

I've always wanted to write a children's book... at least just one if not more. I always have thoughts of grandeur that I will discover a character in my imagination that will have all these beautifully, fun scenarios which would flow onto paper (or keyboard) and become a fantastic book children will fall in love with, with characters they can't resist. Some how I work up all these ideas in my head but when it comes to recording them, nothing comes out... I don't know how to begin. Like my blog, it goes by the wayside because I feel I have nothing important to say or exciting to write about or create. So how does one even begin writing a book? Is there a formula? Is it all at once or jumps around and somehow comes together in pieces. I have a feeling there is no one rule... and for everyone that it is a whole different process, so an intangible art form in the beginning that one hopes can become tangible through the book itself... eventually...