One argument I've seen against prayer to saints is the difference between being able to see (theoretically) your prayer partner(s) here on earth, whereas you cannot see those in heaven. So if you can't see them, you can't call them up and talk to them like you would your best friend who you would ask to pray for you, why do it? Is it the same thing? How can you know these saints to have a relationship with them?
Well, the 'why' I think is covered. More prayer is *good*. If you knew someone here on earth whom you considered to be a holy person, someone who lived a Christian life, who strove with all their might to follow God, wouldn't you ask them to pray for you? Well, that's who the saints are. Only the saints have ended their fight here on earth. They've passed the goal and are with God in heaven.
Prayer to the saints is not like seances, or communicating with spirits in any other fashion. Those are explicitly forbidden in the Bible, and nothing good ever comes of them. Trust me on this one!
"A better way of looking at the presence of the holy departed is found in the story of Christ's Transfiguration. When Peter, James, and John were on the mountaintop with Jesus, they had a momentary glimpse into heavenly realities. Jesus was transfigured before them, and became more radiant than the sun. Elijah and Moses appeared beside him, talking to him. (And don't you wonder what they talked about!) Some kind of loving melody, or exchange, or conversation is going on eternally in heaven, among the holy departed and the angelic host and the undivided Trinity. For a brief moment, these three Apostles glimpsed it."
People find companions in the saints. It happens differently for different people. I know some who study the lives of the saints and find themselves drawn to one in particular. Others find that a saint has much in common with their own lives, or their own troubles. Some have dreams in which the saints come to them, give them messages and the like.
The point is that though the saints are not physically walking around, available on the phone or Skype or anything, they are not dead. It is a different relationship from the one you might have with another person like yourself, but it is entirely possible to have a relationship with them.