
If you want re-tweets, limit your original Twitter messages to 120 characters.
It's not something a lot of folks on twitter think about. You type until you hit the "red zone," going over the 140-character limit imposed upon users by the platform. I particularly applaud those of you who actually tweet the Queen's English, eschewing the "texting code" used by teenagers to quickly communicate via SMS.
Still, as much as I enjoy reading full words on Twitter, many folks using the service are looking to get their message out beyond that first tweet. That means they need to encourage those following them to "re-tweet" the original. Twitter, as well as the companies that make client software for the platform, make this easy to do, offering a "re-tweet" feature. You read something that catches your eye and you want to share it with your friends/followers. Click re-tweet, and off it goes.
There are two styles of re-tweets. Twitter's web interface offers its re-tweet button/feature, where what you want to share is sent out verbatim, giving you credit for the share in the message's metadata. Your involvement between the author of the message and your followers is relegated to a shaded reference below the message.

If you aren't all that interested in being recognized for spreading the word you just read, the current Twitter re-tweet system is easy. As you can see from the tweet above, the entire text of the tweet shows up, but your role in the process is minimized-look below the tweet where it says "Re-tweeted by you."

Many Twitter-savvy folks, however, are willing to re-tweet what you say, they just want it to give them some exposure along with you. This is the old-style of re-tweeting, known as "quoting." Above is a great example of both styles combined. I read a tweet that I thought was funny, so I "quoted" it to my followers. Then @billiegirltoo used the new-style re-tweet method to share it further. Even though I didn't originate this message, subsequent re-tweets of it using the current method go out looking like I wrote it. (The Tweetdeck client is neat in that it shows you the avatars of both folks involved in the message.)
This is what the Twitter-savvy person looks for. They don't want to plagiarize the original thought, but they want their name all over it. If you want to attract re-tweets from folks who are about self-promotion, you have to make the tweet easy for them to quote.
Long tweets are problematic for quoting, because they require those whose help you need to edit your words. There are three possibilities here, and two of them don't work in your favor:
- Re-tweeter takes a look at the length of the tweet and decides they're too busy to bother
- They don't feel comfortable editing your words or you've written something that doesn't edit well
- They see a few things they can delete/shorten and do so
When two out of three possibilities are bad for you, the onus is on you to improve the odds.

Here's a great example of the dilemma. When I clicked re-tweet to share @BasinStRecords' message, It goes well over 140 characters, denoted by the red color of the input box. Can't just hit send. If I'm busy, the most likely result is bullet #1-cancel this and move on. I took the time to try to trim this down, but it was difficult, and I really wasn't happy/comfortable with the final re-tweet.
The best way you can do this is to shorten what you say in the first place. That's why 120 characters is important. When someone "quotes" you, your Twitter ID goes in front of your words. If you re-tweet me, that's an additinal ten characters for "@yatpundit." Re-tweeting "@VisitNewOrleans" eats up the first 16 characters. If @VisitNewOrleans sticks to 120 characters, however, that makes the re-tweet 136, within the limit.
Work with 120 as your limit and get your message out!