But when you pray, go into your [most] private room, and, closing the door, pray to your Father, Who is in secret; and your Father, Who sees in secret, will reward you in the open” Matthew 6:6 Amp 

“If you believe, you will receive whatever you ask for in prayer."
Matthew 21:22

“I can get more out of God by believing Him for one minute than by shouting at Him all night.”  —Smith Wigglesworth

“Heaven must be full of answers to prayers for which no one ever bothered to ask.” —Cameron Thompson

“In the morning I was more engaged in preparing the head than the heart.  This has been frequently my error, and I have always felt the evil of it, especially in prayer.  Reform it, then, O Lord!!  Enlarge my heart, and I shall preach.   —Robert Murray M’Cheyne

“I ought to pray before seeing anyone … I feel it is far better to begin with God – to see His face first – to get my soul near Him before it is near another.” —Robert Murray M’Cheyne

“A man who is intimate with God will never be intimidated by men.”  Leonard Ravenhill

“God will either give you what you ask, or something far better.”  Robert Murray M’Cheyne

“Is prayer your steering wheel or your spare tire?”  Corrie Ten Boom  

“Prayer is not learned in a classroom but in the closet.”  E.M. Bounds

“Talking to men for God is great a thing, but talking to God for men is greater still.”  E.M. Bounds         

BOOKS ON PRAYER:

Principles of Prayer - Charles Finney

Praying Hyde  - Carre

Mighty Prevailing Prayer  - Wesley L. Duewel

Shaping History Through Prayer and Fasting  - Derek Prince