I find YT a great venue when I want to promote an ebook which LISTS several solutions to a problem.
When I create the videos, I give one or two of the "solutions/tips" within the video itself and then end with something like "for more great tips/solutions/whatever, grab a copy of XYZ EBOOK by visiting WEBSITE-NAME".
Likewise, if you have an ebook which teaches you how to do something, walk the viewer through the first few steps within the video and then explain that in order to get the rest of the methods, they can purchase your ebook.
NEVER tell them that they HAVE TO purchase the ebook, always word it as CAN:
i.e. To receive the rest of the instructions, you can purchase my ebook from XXXXXXX
NOT: To receive 13 additional tips, you have to purchase...
If your ebook is strictly informational (such as a biography of someone), explain within the video what subject matters the ebook covers and explain why the consumer should purchase the ebook.
And, always always always offer a special bonus to those who mention "I saw your YT video". It will entice them to view more of your videos in the future, send others to your videos and will make them feel like they're getting something extra.
However, as Ulterios pointed out, NOTHING will help you if you don't have traffic. Once you have mastered the art of obtaining traffic, you can use ANY method to successfully market ANY type of product...