I agree with topquark's methods of promoting your book as they are all non-spamming ways. You could also post links on your Twitter and Facebook accounts, just don't overdo it as it will then be considered spamming. Post a link to the site it is published with (ie: Lulu) and ask your friends to share the link. This will work for both print and ebooks. Another way is to link to it via Pinterest; this seems to be spreading like wildfire.
Something else you could do is set up a book signing at your local library. Offer a discount on your books at that particular event and sign them for buyers. This is presuming you will have printed copies available.
Good luck with your book! I know how difficult it can be to get the word out. Just remember, it takes time. Don't give up if you don't have any sales immediately.