A tweet only has 140 characters; with such a small amount of characters at your disposal, you need to make the most of each one.
The perfect tweet consists of three main parts: your message, a link and blank space. Here's what each section should include:
Message:Call to action: Tell readers what you want them to do.Hashtags: Include one or two to increase your reach among people who don't follow you.Tone: Use your own voice, but in a professional way.Format: Use a mix of headlines, questions and statistics to drive clicks and retweets.
Link:Shortened URLs: Bit.ly links earn the most retweets.
Blank space:Leave room for at least 20 characters at the end of your tweet so retweeters can add comments.
Check out the graphic for more information...
Via Lauren Moss