Start a blog to go along with your ebook. This will involve your readers before your ebook is even completed. As you think of more ideas to include in your ebook, you can blog about them and get comments and feedback from people who will be potentially interested in purchasing your finished ebook.
A blog reaches many people who may not find you through a website or through presentation or teleseminars you may be giving. You will reach people throughout the world that are interested in your topic and what you have to say about it.