I recently read an article by Theologian John Piper. In it he states that most of the time, our prayers should be directed to the Father. "So the pattern that you find almost uniformly - I say almost uniformly - throughout the New Testement is pray to the Father in the name of the Son by the power of the Holy Spirit." He does conclude that we do need to express their personhood (Jesus and the Holy Spirit's), and our love for them as well as asking them to come in fullness. Trinity = One God in three persons (1x1x1=1).