In my own writing, I try to churn out at least two chapters a day. After writing so many chapters, I go back over the chapters I've already written, I go back over all the chapters I've done to do revisions that need to be done, and also to make sure I haven't forgotten some important details. I write in all the details I'd forgotten to add, and revise as I go. Plus, to make sure my writing is what it should be, I've joined a writer's group who does critiques of your work, so this will be greatly helpful in the revision process. I would advise anyone to join a good writers group to sharpen your skills and get constructive criticism of your work. The best one I've found to be the best is the Internet Writing Workshop at http://www.internetwritingworkshop.org/. It's a great group of people, with many critiqueing lists to choose from. There are discussion lists to participate in, where writers can exchange ideas and give pointers on writing. They have a section on writing advice which is invaluable. You should really check it out.
I found this group through a search with bing.com, which is a wonderful search engine. You'll find many writer's groups to choose from, so go through what you see and pick out what's best for you.
When writing from the heart, let the words just flow. You might be surprised how the characters can take over your writing and even surprise you of what you've just written. Thats happened to me several times, and it's wonderful. But remember, write, write, write, every single day. Try to churn out at least two chapters a day, and you're book will be done in no time and ready for revisions.