You don't say what sort of book you've written. If you're thinking of going down the traditional route... I'd say become a famous person. You should have no trouble then. It is very, very, very difficult to get published these days and is a slow slow process. Firstly it's extremely difficult even finding an agent who will read your submission - they get thousands and thousands a year. You now need to have the whole manuscript written and not just first three chapters and a synopsis. Believe me I know how hard it is, my husband's a children's author and it's been a very hard and long journey - over ten years to get into mainstream print. You might try
http://www.printondemand-worldwide.com/ .. I don't want to discourage you. But it really isn't as simple as you might think. You'll have to be tenacious and thick skinned, because rejections hurt! Good luck.