What makes Twitter great for book promotion? Its ability for potential readers to find you and your book is the key. But you need to make yourself discoverable. Three tips that will help:
1. Make sure your Twitter profile reflects your goals. What is your book about, and why are you the expert? Include unique details that relate.
2. Treat Twitter like a cocktail party conversation–be fun and interesting, share useful or entertaining information, and never ever write “buy my book!”
3. Spend most of your time interacting with people who follow and retweet (RT) you, or who favorite (heart) your tweets.
Source:: Caroline McCullagh