Prayer appears to be an ongoing, moment-by-moment part of the life of a Christian (be devoted). It has a sense of urgency (be watchful). And it is a happy exercise (with thanksgiving).
He cannot advocate prayer, talking with God, without connecting it to evangelism, talking with people. This takes two forms. Pray for an open door to speak -- opportunity. And, be wise, redeeming those opportunities, having gracious speech. That is, create the doors you pray for. Paul says, ". . . as it is necessary for me to speak" and tells us to be prepared for, ". . . how it is necessary to answer."
"Let your speech be always with grace, seasoned with salt." What a great description of ideal speech for someone who is a Christian. Especially if you believe Jesus' words, "For from the abundance of the heart the mouth speaks." The heart is where the grace and seasoning come from!
Again, this rich network of relationships is the church. The long and descriptive list of friends reminds us that people are the church. Paul not only greets his friends, but reminds people of their relationships with other people. Relationships really matter.