It is common, in some circles, to hear that there are no particular requirements for the words of our prayers. We can pray however we like. This advice is meant as encouragement. It is true as far as it goes. It does not go very far.
When his followers asked him to teach them to pray, Jesus gave us a very clear answer:
Our Father, who art in heaven,
hallowed be thy name,
thy kingdom come,
thy will be done,
on earth as it is in heaven.
Give us this day our daily bread;
and forgive us our debts,
as we forgive our debtors;
and lead us not into temptation,
but deliver us from evil.
For thine is the kingdom,
and the power, and the glory,
We give this prayer the name 'The Lord's Prayer.' It is his prayer because Jesus gave it to us. It is also the disciples prayer because he gave it to us. It is his gift to us. Jesus was not giving us just a set of words to recite in prayer. He gave us a pattern of prayer. It has a beginning, a middle, and an end. The beginning orients us to God: Our Father, who art in heaven. We are praying to God the Father with Jesus, his Son. The middle is a set of six requests. The end is worship: For thine is the kingdom and the power and the glory. The pattern is meant to shape our prayer. By shaping our prayer, it shapes our heart.
First, notice that Jesus honors the request of his disciples. He is not simply teaching us a prayer, but how to pray. When the disciples ask Jesus to teach them how to pray, it is while Jesus is praying. He immediately gives them a clear answer: "When you pray, say...." Jesus answers a lot of people with parables. Parables are oblique answers to a question. But when we simply and directly ask Jesus to teach us how to speak with his Father, he gives us a clear and profound answer.
You can find the Lord's Prayer in Luke 11 and Matthew 6. This is the first post on prayer and on the Lord's prayer. There will be further opportunity to dive deeper and understand Jesus' prayer more fully.