You can't argue that great use of social media for your agency (business) is both an art form and a science. Chances are you want to increase your voice in the social space and understanding how to use both artistic creativity combined with science will improve your ability to be shared.
1) Quote or ReTweet: I have become a huge fan of the Quote feature especially in those instances that I want to add my thoughts about why I'm sharing the information.
2) If You Don't Ask, You Don't Get: Be willing to ask your audience to retweet you. While "Please RT" is good, actually spelling it out is even better, "Please RETWEET."
3) Make it Valuable: While some tweets can be 'just for fun' or 'just because', nothing is as important to sharing as the actual content you put out. Put out great content that is value based on your audience needs and you'll see more shares.
4) What's In A Number: If your tweet has a number in it, use the numerical value instead of the long version. Using a number shows an increase of 17% in retweets, not seventeen percent.
5) Think About News and Instructions: Everyone wants to be on the front edge of sharing great information that is relevant or helpful to others. The most popular things people want to share are news, instructional information, entertainment, opinions and products.
6) Timing: If your audience is most active online at 2:00pm on a Saturday, that would be a great time to put out your content for maximum shares. Commuter times, weekends, lunch time are all considerations to help you make your best time. Your own analytics will tell you as well if you're paying attention.
7) Picture This: Adding pictures to your tweets can dramatically increase the retweets. Pictures also can tell your story for you leaving you with less typing to get your thoughts across.
8) Hashtags: Like pictures, good hashtags can slice your character count. They can act like chapters in a book explaining the content without using a lot of words. Be careful on how many you use. 2-3 maximum per tweet. Going beyond that can make your tweet look like spam.
9) Link It: Using link in your tweet has shown positive retweets and better awareness of what you are trying to message. Placement matters here as well. Links that are between 75 and 90 percent of the way into a tweet increases their purpose.
10) Be a Retweeter: One of the cornerstones of social interaction is 'returning the favor'. Want to get retweets? Retweet others AND GIVE CREDIT. When you see other people's great information share it, but make sure you include that person in your tweet as a "@ via", "@mention" or just an organic retweet itself.