Book writing tip No. 1: Don't write if there's some other way
Probably the best book writing tip one can give is not to write a book in the first place. If there is any other way of fulfilling your dreams or satisfying your needs, try them first. Book writing is time- and -energy consuming while there is no clear way to know what to do to achieve success. Apparently, this tip doesn't tell about a situation when you are asked to write a book rather than writing a book and then trying to sell it.
Book writing tip No. 2: Read before you write
Another book writing tip that will make your job much easier and your book much better: do not start writing until you've read all (or almost all) that has been published on the subject. If you don't follow this tip, (a) you will lack knowledge on the subject - even if you think you know everything, there are hundreds small details you should know, (b) you will probably have problems while writing – no right words at hand, problems with a plot etc. or (c) you will only too late find out that someone else has done it before you and your book will only be a poorly (though independent-made) clone.
Book writing tip No. 3: Simple plot, complex language
The most powerful thing in the book is not a plot – it is really hard to make something really new – but the language and details you use. Book writing is not really about creating a unique story, but about making an ordinary story unique. See “The World According To Garp” or “Harry Angel” if you don't believe - their plots are simple, yet both books have become extremely successful. The real power lies in language used and the characters. That's a tip most beginning writers miss – they concentrate more on a plot rather than characters. Apparently such “from zero to hero” writers as J. K. Rowling followed this book writing tip – the plots of “Harry Potter” books are simple, it's the characters and magic gadgetry that are interesting.
Book writing tip No. 4: Short stories first, novels later
The last book writing tip, very useful if you really intend to become a writer – don't write a novel, start from short stories first. For one, it will be easier to publish it somewhere (even on the Internet) and use it later as a lever when you try to convince an editor to accept and publish your book. What's more, it is easier to write a short story than a full-length novel. There is just less room for mistakes.