As an indie author, you might spend more time tweeting about your books than actually writing them. Social media is your best avenue for marketing, and Twitter is an incredibly popular social media site. But tweeting about your books isn't easy...because you've got to figure out what to tweet about.
This Space for Rent
You can't tweet "buy this book" all day long, because who's going to click on that? You tweet something like that all the time, and you'll just get a bunch of people who unfollow you all the time. If you really want people to buy your books, you've got to use your tweets to make a case for yourself.
And you need to a spanking good job, too...because you've got a very limited amount of space.