Isaiah foretold a voice crying in the wilderness, "Prepare the way of the Lord!" Mark links John the Baptizer to this prophecy, with John's proclamation that one is coming after him whose sandals he is not fit to untie.
Conveniently, Jesus arrives on the scene and gets baptized. Mark records that coming out of the water, Jesus has a vision and hears a voice from Heaven. He then goes out and has a wilderness experience.
Coming back from the desert, He calls Simon, Andrew, James and John, who drop their nets and tag along with nary a goodbye. They go to Capernaum, where Jesus causes a local stir by casting out demons and healing a leper. He tries to keep them quiet about who he is, but rumors begin to circulate.
So far the picture we have of Jesus is of a poor, simple (albeit very charismatic) preacher and folk-healer - a hard act to follow, though that doesn't keep some from trying.