The key to prayer is to know

Get totally clear in your heart, mind, body, soul and will - as to what is God's will or God's way - then PRAY FOR THAT - and you can absolutely know you receive it, which manifests it.

Consider these 2 scriptures (from YLT):

1 John 5:13-15 These things I did write to you who are believing in the name of the Son of God, that ye may know that life ye have age-during, and that ye may believe in the name of the Son of God. And this is the boldness that we have toward Him, that if anything we may ask according to his will, He doth hear us, and if we have known that He doth hear us, whatever we may ask, we have known that we have the requests that we have requested from Him.
The chapter then goes on to explain we can pray in confidence that God will give life to those for whom you pray and forgive, because you're praying and functioning in His will.

NIV: This is the confidence we have in approaching God: that if we ask anything according to his will, he hears us. And if we know that he hears us—whatever we ask--we know that we have what we asked of him.

Proverbs 3:1-8 My son! my law forget not, And my commands let thy heart keep, For length of days and years, Life and peace they do add to thee. Let not kindness and truth forsake thee, Bind them on thy neck, Write them on the tablet of thy heart, And find grace and good understanding In the eyes of God and man. Trust unto Jehovah with all thy heart, And unto thine own understanding lean not. In all thy ways know thou Him, And He doth make straight thy paths. Be not wise in thine own eyes, Fear Jehovah, and turn aside from evil. Healing it is to thy navel, And moistening to thy bones.

​NOW, meditate on these 2 prayers of King David:

2 Samuel 7 -- Nathan the Prophet tells David of God's promise to David. David agrees to receive God's promise, and David worships. David's prayer concludes as follows (at v 27-29):
     “Lord Almighty, God of Israel, you have revealed this to your servant, saying, ‘I will build a house for you.’ So your servant has found courage to pray this prayer to you. Sovereign Lord, you are God! Your covenant is trustworthy, and you have promised these good things to your servant. Now be pleased to bless the house of your servant, that it may continue forever in your sight; for you, Sovereign Lord, have spoken, and with your blessing the house of your servant will be blessed forever.”
     God revealed His will, David received it by faith and prayed for what God directed. Its an agreeing between God and man, a communion of covenant, established by faith (trust/belief)

2 Samuel 12 -- Nathan the Prophet tells David his son will die because of David's transgression (adultery with Bathsheeba and murder of Uriah). David repents, fasts and prays for 7 days, trying to persuade God to let the child live. God refuses David's prayer. The child dies. And David worships.
​       God revealed his judgment, David didn't like it, didn't get what he wanted, but David goes to the House of God and worships God. Praying & fasting while it is happening. Worshiping when it is over. In all things, humbly acknowledging God is God and His ways are just.