6"But you, when you pray, (H)go into your inner room, close your door and pray to your Father who is in secret, and (I)your Father who sees what is done in secret will reward you. Matthew 6:6
23"Moreover, as for me, (A)far be it from me that I should sin against the LORD by ceasing to pray for you; but (B)I will instruct you in the good and right way. 1 Samuel 12:23
In my own life, these scriptures have helped me to be constant in prayer and powerful in seeing requests answered. This is not a magic formula to get your selfish requests answered however. If you want to see God working in your life to accomplish His will through you, then you will pray things that God wants to happen (salvation, repentance, changed lives, His glory known).
Don't pray for his will in your life if you are unwilling to obey him in your daily life. Don't presume that you deserve better or are better than anyone else. You must pray for God to work in other people's life and pray unselfishly.
An example is when someone asks you to pray for them that you know they are godly persons. You should pray for that request until God answers it for them. If someone you know is unsaved, you should make sure you are saved first (Romans 8:16, Romans 8:14) and then pray for their salvation. Another example is when someone mentions to you some scripture that they think has been impactful in their life or some doctrine that you may never have heard about or something that you should go and study. You will hinder your spiritual growth if you do not make an effort to understand that concept.
Also, I have found that people may not ask you to pray for them but need prayer. For example, a group of guys that I meet with have been studying the Bible for a while but haven't been seeing God's power displayed. I know the leader of the group is praying for the guys so I decide to join in praying for the same thing the group leader is praying for (Matthew 18:20). This verse is talking about praying in groups and it is certainly effective to pray in groups but I think the verse is talking about two brothers earnestly praying for the same thing with the same desire in mind. We often pray in groups thinking that is the magical formula. Simply, I don't think that is very effective unless the people in the group are Christians and are praying for the same thing and are doing it with unselfish motives.
So, as I have been praying more, I have been seeing the working of God more strongly among my family and friends. Hopefully, these things will help you as well.