Twitter is all about timing – unlike Facebook, where users spend ample time on each other's profiles, tweets are generally read when they are posted and seen on the homepage timeline. Now, Twitter is expanding its Promoted Tweets platform to let advertisers get their tweets displayed in certain users' timelines, and marketers may like the increased visibility this provides on the microblogging site.

In its official blog, Twitter announced that it is testing the syndication of Promoted Tweets with account holders who access their tweets through its partner, HootSuite. Not all HootSuite users will see Promoted Tweets in their timelines and those who do will see unique promoted messages. Twitter emphasizes that it will display ads that are relevant to individual users.

"We use several signals to determine a Promoted Tweet's relevance to a user, including the public list of whom they follow. We will expand the rollout only when we feel we're delivering a high-quality user experience."

Whether marketers use Promoted Tweets or not, the message is clear that relevant content is key to catching users' interest on Twitter. When trying to decide which type of tweets might garner retweets, it may be wise to consider the results of a recent CNN POWNAR study, which reveals that most online news-sharing happens at social sites, and that 27 percent of consumers favor brands affiliated with news.