Why did Peter follow Jesus?
Peter followed Jesus first because his brother, Andrew, told him that he and John, Peter's fellow fisherman, had found the Messiah (John 1:41-42), so initially he went out of curiosity. When he met Jesus, he was given a nickname, which indicated what kind of man he would become. They saw Jesus do many miracles, including healing Peter's mother-in-law (Luke 4:38-40).
At some point Peter returned to his fishing business and when Jesus came by teaching (Luke 5:1-3), Peter became more deeply convicted. Peter was more than willing to let Jesus use his boat to teach, but then when the teaching had finished he had asked Peter to push out and cast out the nets again, even it was not the usual time to fish. They had already washed out the nets after having worked through the night (the usual time to fish in that region). Peter submits to Jesus' request because of the miracles, teaching and evidence he had seen earlier; but as of yet Peter didn't fully grasp who Jesus was (Luke 5:5). He casts out the nets again, the catch is so large that the nets begin to break, and Peter and Andrew needed help dragging them in (Luke 5:6-7). It was at this moment that Peter realized who Jesus must be. "But when Simon Peter saw that, he fell down at Jesus' feet, saying, "Go away from me Lord, for I am a sinful man!" (Luke 5:8). Jesus then calls Peter and tells him to follow, promising to make him a fisher of men (Luke 5:9-11).
Until this point Peter partially followed Jesus. He was still working the boats and still living a regular life. But when Jesus told him to follow, Peter followed completely. He left the biggest catch of his entire life behind and everything he held dear to be a disciple of Jesus (Luke 18:27-30). He learned that Jesus came to save the lost the sinners (Luke 5:31-32).
Even after this, there were many times when Peter wavered in his faith, even though he had already decided follow Jesus. The major turning point was his complete commitment to die for God after Jesus was resurrected. We mature as we go along in our faith, and Peter was no different. Realization of who God really is hits us square in the face many times, as Peter experienced. In the end, we must give all to follow God. It might cost us our family, work or even our lives, but there is no cost too great to follow Christ (John 21:18-19).