I don't believe there's a secret to powerful prayers. Except this:
(James 5:16p NIV) The prayer of a righteous man is powerful and effective.
Be a righteous man. And pray for things that are within the will of God. There are no magic words to get you what you want. God can't be manipulated. God already knows your heart and what He plans to do. An insincere person who tries to manipulate God deserves nothing from God.