I like this entry in the Handbook of Bible Application:-

Sometimes we wonder how to pray for missionaries and other leaders we have never met. Paul had never met the Colossians, but he faithfully prayed for them. His prayers teach us how to pray for others, whether we know them or not. We can request that they

1. understand God’s will,
2. gain spiritual wisdom,
3. please and honor God,
4. bear good fruit,
5. grow in the knowledge of God,
6. be filled with God’s strength,
7. have great endurance and patience,
8. stay full of Christ’s joy, and
9. give thanks always

All believers have these same basic needs. When you don’t know how to pray for someone, use Paul’s prayer pattern for the Colossians (Col 1:3ff).