What Missionaries Do
Most of the Church's missionaries are around twenty years old, though many members also volunteer to serve after they've retired. All prospective missionaries turn in applications to Church headquarters and they receive a call to a specific mission around the world. They spend a few weeks in a training center where some of them learn a new language and all of them rigorously study and practice teaching the gospel. Then they set off to their assigned locations and begin their service. Missionaries' lives are completely dedicated to sharing the gospel of Jesus Christ. They pay their own way and put off school, dating and work for two years in order to focus entirely on doing the Lord's work.
A common morning for a missionary might consist of waking up at 6:30 a.m., studying the scriptures, and meeting new people to share the gospel with. The afternoon might include discussing gospel lessons with people they meet and volunteering for service in the community. A good night has them teaching the gospel to interested individuals and helping them learn and keep God's commandments or attending a baptismal service for someone who's decided to join the Church. They return home around 9:30 p.m. and fall into bed, usually exhausted and happy.
Read more at http://mormon.org/missionary-work.