Besides making your tweets interesting, here are some tricks to get people to retweet you more...
1. Don't tweet the same thing over and over again.
I don't use any sites where I schedule tweets ahead of time, so they can be posted for me. If you see me tweeting something it means I was at my computer during that very moment typing it up. While I think there is nothing wrong with scheduling tweets, if you're going to do it, make sure no one can tell that you do.
There's this guy that I follow and I remember laughing at a quote he posted and retweeting it. The thing is, I saw that quote again the next day and the day after that and the day after that. He had obviously scheduled that same quote to be posted over and over again. I almost unfollowed him for it because I didn't feel like he was really there. I knew he used some web-site to post his thoughts, while I wanted to talk to a person.
I didn't unfollow him, but I never retweeted him again. He's already retweeting himself, so he doesn't need me to help him with it.
Even announcements of your book can be reworded every time. One day, talk about how cheap your book is and provide a link to it. Another day, post a link to a blog review. You can also post various quotes from the book or reviews, changing them daily. Or write a new short blurb every time. Write interesting facts about your book or announce a price drop.
Change it and don't do it too often, so people feel like they are talking to a person instead of a robot.
2. Tweet Quotes or Funny Thoughts
Liuks are nice and I click on them occasionally when I'm on twitter, but far more than anything, I enjoy reading a short sentence about people's thoughts or a funny quote they came across.
On twitter, everything happens so quickly that even someone with a great attention span has trouble concentrating on any tweet for long.
So don't post links all the time. Break it up with your thoughts or silly ideas you've come across. People will remember you more and be entertained by you. They'll be more likely to retweet you and read your links when those do show-up.
3. Make it into a game.
One way I get a lot of retweets is by making my tweets into a game. "Retweet this if you believe in ghosts, favorite it if you disagree." People love to give their opinions and it only takes a second for them to do so. So they'll love participating in this challenge and you'll get several retweets about it!
Relate the question to you as a person and what you are trying to represent on twitter. For instance, I am a writer and I want to reach readers, so I might ask something like "Retweet if you love e-books, favorite if you prefer paperback." I make the retweet about e-books because all I have available is e-books and I want people who like e-books and their friends to read my tweet.
Try it! It's fun to read people's opinions too!
4. Retweet other people
People are more open-minded to giving back to people who gave to them first as well.
And a list of things not to do . . .
1. Do not beg for retweets
It makes you seem desperate. Not only that, but people might judge you. Why should I retweet someone who has to beg to get retweets?
2. Do not demand retweets
If you demand that someone retweet you because you retweet them all the time (or feel that they owe you a favor in some way), then all you are going to do is lose a friendship. They'll think you have a bad attitude. Do things for others not expecting anything in return and they'll often give you stuff in return anyway. But not everyone will.