The Nazirite vow is described in Numbers 6:1-12, where it is a temporary vow of separation to God. Samson is unique in being set apart from birth. In typical Old Testament style, the signs of separation are external and will be no guarantee of godliness. But the lesson is clear: The person God uses ought to be different from the world.
The New Testament deepens the meaning of separation, emphasizing inner purity and outer righteousness. The separation of the New Testament is not immediately obvious (as uncut hair would be), but involves the entire life of the person.
All Christians are set apart for God, for that is the meaning of the word holy. Infant baptism symbolizes that our children are set apart for God; our children should be reminded regularly that they should be different from many in the world. Teenagers will need to sort through the meaning of holiness in the present age. Adults ask for guidance, as the way of holiness is not always as simple as controlling what you eat and drink and how you cut your hair.
We should not despair of holiness, however, for we have a fuller measure of the Holy Spirit than Samson had.
Father, guide us by means of the Bible, the church and our families, as we try to understand what it means to be set apart in Christ. In His name. Amen.