One of the most important conditions for effective prayer - is confidence in God. In a word, Faith.
Many believers in Christ, especially in the early stages of following Him, do not fully understand how faith functions. They feel like something bobbing along on the ocean of life, and they have no steering mechanism, nothing solid to put their feet down on, nor anything strong and stable to hang onto. So we panic because we feel out of control, wildly we start grabbing at anything and anyone that has some stability. Some say they feel blind-folded; they can't see where they are in life.
This is where we need to learn - confidence in God. The kind of faith that honours God. God honours such faith. The security we must latch onto is God Himself.
We are weak but He is strong. When we let go and stop struggling so hard to do good, to please - just believing God will work it out, - then we find that God Himself rescues us, scooping us up, and holding us in His arms. We feel safe. We believe God will work out the unknown parts for our good - and we start praising Him!
Jesus' brother James stresses in his letter, "If any of you lacks wisdom, he should ask God, who gives generously to all without finding fault and it will be given to him. But when he asks, he must believe and not doubt, because he who doubts is like a wave of the sea, blown and tossed by the wind. That man should not think he will receive anything from the Lord; he is a double-minded man, unstable in all he does." (James 1:5-8 NIV)
At the very least we must believe that God exists, and He rewards those who earnestly desire to connect with Him. (See Hebrews 11:6). The more we learn to know of God's power and authority, the deeper, broader our faith will grow.
There is a natural faith that even unbelievers can exert, such as - this car will take them from here to there. Here though, we are talking of a spiritual faith, that is given to truly born-again Christians. We have all received the ability to trust God, but this is like a baby's leg muscles; they are there - but they need to be exercised and used over a longer period of time, before we can see that baby walking or running.
Are you convinced that you have this faith - this confidence in God, and in His promises?
Do you exercise your confidence in God? Start, no matter how weak or naive you feel. Read and study the Bible, and keep asking God to help you to trust Him, and you will find that small faith gets up, toddles a while, and then begins to walk.
As already implied, faith is confidence in God, and a study of Romans helps us understand the importance of hearing God's Word.
So then faith comes by hearing, and hearing by the word of God. (Romans 10:17 NKJV)
We can listen to God's Word read in church, but better still, we can read it for ourselves, study it, grasp that God means what He says, and believe it. The more we believe God's Word, the more faith we will have that He will keep His Word. And there is our confidence in God!
Now, when we ask for something that God has promised, and we are confident He will do it, we shall pray effectively and with great results!