Here’s some interesting data from Dan Zarrella of Hubspot on optimizing your tweets in order to increase your click-through rate of the links you post on Twitter.
Placing your links about a quarter way through your tweet, using more verbs and adverbs, tweeting late in the day and at weekends appears to increase the likelihood of click-through.
Health Care Social Media 
How intriguing. Some I would have figured, but some I would have never guessed. Great find.