I've managed to adhere to at least one of these - marry someone you love and who thinks you being a writer's a good idea. My favorite, because it is simultaneously the simplest yet the most difficult, is this:
The way to write a book is to actually write a book. A pen is useful, typing is also good. Keep putting words on the page. Anne Enright offers this sage advice.
While we're on this subject, I may as well admit that I currently have two copies of bird by bird by Anne Lamott on my bookshelves. I love this book. If you haven't had the pleasure, read it. I've read it so many times that I've lost count. But, reading about writing a book is absolutely not the same thing as actually writing one. Not even close. Neither is blogging about writing a book, so I'm going to take Anne's advice and go write something.