Writing a book

... so I have been toying with the idea of writing a book. I have really no concept of how to get started, hence the 8 books next to my desk telling me how to write a book that I haven't picked up.  Dotted around my computers are various files with names saying "i must write', ideas for stories' etc.  Not much in them.  I haven't settled to what medium i want to write in yet and that is as easy as saying do I want to start typing away on the computer or would by hand be better as you have more scope to doodle in the margins.  How am I going to write when I can't even decide how to write first.  Then I have all these ideas for different books.  I have started approx 3 and I don't know that if starting them means writing a title and then a chapter heading and then 'once upon a time...'.  It doesn't seem like a lot does it?  It is always very confusing and then I skip through a book in about 1/2 day and read the author's thank you's which always say how hard it was and thank you to everyone feeding them and looking after their children, and I think what the hell goes on... then i get scared that no one will like my idea and so on and so forth.  i don't seem to have a problem keeping my mouth shut, I wish it would just show up on paper a bit easier.