Memorizing the Lord's Prayer—which is a bit of a misnomer; it should be "The Disciples' Prayer" or "The Model Prayer"—is a wonderful thing to do. Parents should make it their aim to teach it to their children. But unlike many in nominal Christianity, we need to go further and teach our children that the prayer is not one to be mindlessly repeated but a guideline for our personal, private prayers to "our Father in heaven." It maps out the general attitude and subjects of prayer that we should take to heart and cut deeply into our memories.
It is a wonder that so few who frequently use Matthew 6:9-13 both publically and privately know what Jesus says—no, commands—in the immediately preceding verses:
And when you pray, you shall not be like the hypocrites. For they love to pray standing in the synagogues and on the corners of the streets, that they may be seen by men. Assuredly, I say to you, they have their reward. But you, when you pray, go into your room, and when you have shut your door, pray to your Father who is in the secret place; and your Father who sees in secret will reward you openly. And when you pray, do not use vain repetitions as the heathen do. For they think that they will be heard for their many words. Therefore do not be like them. For your Father knows the things you have need of before you ask Him. (Matthew 6:5-8)
Christ plainly says that public prayers made expressly to be seen by others is hypocritical, and prayers that are repeated vainly (meaning "carelessly," "uselessly," or "thoughtlessly") are heathen! Obviously, this does not mean that He forbids public prayer; there are many examples of proper public prayer in Scripture (see, for example, I Kings 8:22-53; Ezra 9:6-15; Nehemiah 9:5-38; John 17:1-26; etc.). Public prayer is a necessary part of opening and closing religious services. What Jesus denounces is making a show of praying to enhance one's reputation as a "religious" or "righteous" person, as well as repetitious, canned prayers and overlong, tedious prayers.
Overall, Jesus warns us against two mistakes when praying: making them about us and making them meaningless. Doing either (or both) will ruin their effectiveness and actually work at cross-purposes to spiritual growth. When we pray, we need to remember that it is a formal conversation with the divine Governor of the Universe. We have not entered His court for our own gratification and glory. We certainly do not want to bore Him by endlessly repeating the same five words or giving Him the expanded War and Peace version of our pitiful lives. To the contrary, we are before Him to praise Him, to thank Him, to beseech Him for help both for others and ourselves, and to praise and thank Him. I repeat myself for emphasis.
What would we think of a friend who came to the front door each morning, and upon opening it to admit him, we heard him say the exact same thing that he had said the past 532 straight mornings, droning on for half an hour without coming up for air? We might love him as a friend, but we would surely think he was a bit strange and wasting our time with his endless repetitions. We would soon tune out his robotic, one-sided conversation.
We are blessed that God is far more patient and understanding with us than we would be to such a bore. He listens to our petitions whether we are eloquent or mind-numbingly incoherent (see Romans 8:26). Yet, notice that Jesus tells the disciples—us—that the Father knows what we need before we ask Him. We are not springing anything on Him that He has not already figured out.
So there is no need for us to meander, be vague, or employ some kind of rhetorical device that is "guaranteed" to convince Him that He has to intervene right away. There is no need to try to impress Him with our knowledge or persuasiveness or righteousness. He wants us to be ourselves and to speak with Him as family members do—with, of course, the proper reverence for who He is.
What is most important—what He is looking for—is a "poor and . . . contrite spirit, and [one] who trembles at My word" (Isaiah 66:2). If the attitude is humble, focused on God's will and His plan for us, He will hear and respond. More importantly, we will be drawing closer to Him and taking on aspects of His character that are so essential to Christian life and the Kingdom of God.