The answer is twofold, in my opinion, (1) choose your words carefully so as to best capture the essence of the message to make it compelling AND (2) include a call to action.
Since the readership of your tweet (your followers, for the most part) is done serendipitously, you can not always be sure that your message will be read. In any case, a good idea may be to time the post (tweet) for lunch time or at the end of the day, when your followers might be taking a break from their work, and dipping into the Twitter stream.
So, you could pre-schedule your tweets. There are several tools to do this with. For example, here are some articles that review these tools: