Philip found it hard to keep quiet about something that he thought other people should know about. It wasn't a part of his personality to find something out and keep it to himself. Once he had become a follower and disciple of Jesus, this tendency led him to guide others to God and introduce them to the Lord he had met and become devoted to. It had all began with Nathaniel. "Nathaniel," Philip called, "you must meet the man whom I met and know him as I am coming to know him." Of course, Nathaniel had taken the opportunity to be introduced and followed shortly thereafter in Philip's footsteps as a disciple of Jesus. It was second nature for Philip to share Jesus with Nathaniel and he never thought twice about it.
As Philip followed after Jesus he had another opportunity to introduce people to Jesus in a grander and more impressive way. Philip spoke Greek fluently and was able to use this skill for the Kingdom when Jesus and his disciples found themselves among a community of Greek-speaking Jews. A group of them approached Philip at the perimeter of the crowd and said, "Sir, we want to meet Jesus." Philip was instantly excited about being able to make this important introduction again. He tapped Andrew on the shoulder and said, "These men want to meet Jesus!" Andrew and Peter ushered them through the crowd and introduced them to the man who was ushering in a Kingdom founded on forgiveness and redemption through the power of love. Because of Philip's eagerness and gifts, he was able to introduce them to Jesus and his Kingdom. Philip had, once again, been a guide for the wandering.
We don't know what Philip did specifically when Jesus was arrested and crucified. We know that like the other disciples, he fled and avoided the punishment that he and the others anticipated for associating with the condemned Lord. Further, we know that he was present when Jesus appeared again unto the twelve and when the Holy Spirit descended upon them all at Pentecost. Through Jesus' death, burial, and resurrection Philip--the great guide--was introduced to the power of sacrificial love and redemptive forgiveness for the broken and the sinful. It was this introduction that had the greatest impact.
Philip himself traveled to Greece, Syria, and Phrygia to share the news. While there, he began preaching the Gospel of love for enemies and forgiveness for sinners that he had been introduced to by Jesus. He began the process of slowly introducing more and more people to the one who had come, died to forgive sins and inaugurate a new Kingdom, and had promised to come again. He did miracles and attracted a good deal of attention. All of this went reasonably well for some time until he introduced the wife of the proconsul of Hierapolis to Jesus. For this offense, he was arrested and crucified upside down as a deterrent to any other who would dare try to tell the same story of a God who became human and died to reintroduce the lost sheep of the flock to life and truth.