This is a very helpful post on the Elance blog. Jeff Haden a freelance writer give his tips and advice on working with a freelance writer when outsourcing your written project.
Some of his advice is similar to what I outlined in my article on "Tips on picking a provider " If you haven't read it here is the link.
Tips on picking an outsourcing provider  read more »

Tip 1: One task at a time.

Outsource a single task when outsourcing for the first time rather than going for everything at once. It ensures you are comfortable with the process and you get people who are trained along the way rather then just dumping it on them. You will lose track of what you are doing. For example you want an ebook written, graphics for the cover, a website designed and put together to promote your book. Do one thing at a time. Go for a single task then work your way up to finding someone to do everything.