1 Corinthians 16:20

All the brethren greet you. Greet ye one another with an holy kiss (KJV)

Then: A normal way of greeting each other was by use of a kiss. In Paul's calling it "holy," he's lifts the importance of interpersonal greetings to that of the friendship between Christ and the church. Baker (p. 248) explains that a holy kiss was not part of church liturgy until the days of Justin (100 - 165 AD).

Now: We greet with handshakes and maybe a cheek-to-cheek hug. Actions change; sentiments don't.