“The right way.” I send out announcements and ask friends to share them. I have about 7000 people who get my newsletter, another 5000 friends on Facebook, 20,000 on Twitter, a few thousand more fans on Facebook, and so on. So I can make a pretty decent splash, and if my friends do the same, we can make huge waves! Books I promote generally hit #1 on Amazon in one or more categories.
“The right time.” I like to recommend books on their release day or shortly before. With many books, if you recommend them three months before the book comes out, readers won’t want to wait that long. It’s an impulse buy. On the other hand, some people are happy to buy a book early and wait for it, so letting people know a book is coming in a few days usually works well.