Discussions on prayer often make me. . . leery. Why? Because too often people approach prayer as though it's point is the Manipulation of God - as though if I just pray hard enough, or enough people pray, or if I'm righteous enough and ask God then X will happen, where X is anything from healing to a Mercedes Benz.
God does not need us to tell Him what is good for us. God does not need our instruction. Rather, we pray because we are in need of His instruction - because we need to place ourselves once again under His Word - and so we pray -- and all right and good prayer is simply speaking back to God His Own Word - to pray as He has taught us, to speak ourselves His own promises back to Him.
Prayer is applying the Word of God to one's own self. When I am ill (or those I love am ill), I pray for their health and healing if it be God's will, and I am reminded that God is not only the Author of life, but it's Preserver, and He does indeed love His creation, and will care for it in a way that is most excellent.
When I pray for temporal blessings (for myself or others), I am reminded that all that I have comes from God without any merit or worth in me, but simply from His Divine Fatherly goodness and love - and so once again I am reminded that He indeed knows what blessings are good for me, and indeed, what blessings would turn on account of sin into a burden, even a curse, too great to bear.
When I pray for mercy - I am pointed to Christ Jesus, the One who has come to win mercy upon the Cross. When I pray for joy, I am reminded of the One who came to win for me joy. When I pray for my loved ones, I am pointed to the One who blessed me with those loved ones. When I pray for the lost, I am pointed again to the mercy of the Good Shepherd who cares and seeks even the lost.
In all things, when our prayer is centered in the Word, it sees that we are centered in the Word. Prayer is not the manipulation of God - it is learning to place all things in the hands of God, trusting in Him. It is learning that "Thy will be done" is good, for the will of God is always good to His children.
That is the point of prayer.