The 113th Congress of the Senate (2013-2015) comprises 53 Democrats, 45 Republicans and two independents, thus it can be said that the Democrats, the majority party, control the Senate. The Vice President of the United States presides over the Senate but does not vote unless it’s to break a tie.
In 2014, the President of the Senate is Joe Biden. Typically his presiding officer responsibilities, other than ceremonial, are delegated to junior senators in rotating shifts so that they can learn Senate procedure. Typical duties include calling on senators to speak and announcing results of votes. Senate Party Leaders are elected by their political parties and are responsible for scheduling debates and votes.