A book of my own

Any suggestions for a person who is about to write their own book? Theme will be sci-fi, because I feel that every other theme has been covered by another writer already.

Won't be anything like things that already exist like Star Wars. I'm planning on writing something completely new, something that people will find interesting to read.

I've never written a book before though. Are there things that I should look out for? Applications that help out in writing a book, or should I just bring out the good old Microsoft Word?

>>8
The thing is, I want something that is sci-fi, but still fun enough for most people to read it. I want the kind of book that gets international publication and fame.