I hope that some of these ideas will help. I work for a publishing company in Australia, so hopefully a few extra suggestions will help. As it is 4am in the morning here I will make some quick points before attempting to cure my insomnia! These points are based on an assumption that you do not have formal training. Writing a book is the merging of 2 skills - expertise + the ability to comunicate. Everyone can write but not everyone can communicate.
A few suggestions.
1. Buy a book on how to write a book. You can get them on how to write a particular type of book, whether it be romance, newspaper articles, technical books, etc.
2. Write. Write. Write. Everyday. And cull heavily. If you decide to write first in the Journal form as Paperbear suggests, the culling will be heavy.
3. Know your audience and the know the style you wish to write. That means reading. If you write a romance novel, you would read other romance novels in order to immerce yourself in that style & learn from it. So read other publications aimed at the novice & learn. Look for how they use language, pictures, construct sentences, paragraphs, chapters etc. And do this outside the koi hobby as well. If you pick up a book aimed at a novice bonsai hobbiest and it teaches you straight away & easily, then it can also teach you how to communicate to any audience.
4. Publish smaller articles in reputable magazines. This will give you experience. It will also mean that when your book is finally published, you already have some credibility.
5. Dont worry too much about the cover and title right now. Unless you self-publish, you may not get to choose.
6. Have a plan. Every story has a beginning, middle and end.
7. Give it to others to review. Not friends, but those willing to tell you the truth. This is another reason to be published with smaller articles in reputable magazines
I am off to hopefully find sleep. I really think the best advice you can follow is get that book on how to write a book. It will teach you much more than I can in this post.
Oh, one more thing. You will have put your heart into this, feel proud and feel that its perfect. But once you give it to a book publisher, expect the it to go through many changes. The publisher wants to sell your book, how you feel is secondary.
My intention is not to dull your enthusiasm. Writing can be hard work.
I hope this helps
BB