With regards to prayer, without deviating into arguments or discussions about who various people pray to or through, I believe that many of us experience problems in our prayer life account of our own activities and our own relationship with God/Christ/Holy Spirit. Many talk about Christ as a totally different person from God or God's Holy Spirit but the three are three forms of ministry from one single God.
Each Christian should have and does have the ability to approach God with their own desires and request and the writings of Paul in Romans 8 expound on the Holy Spirit's ministry unto the Christian and one of those ministries is helping us voice our needs and desires unto God. Many Christians also allow their own sins to cloudy the relationship between God and man/woman. Others do not have the confidence that their prayers will be heard, account of their own limited faith.
Christ, Himself, instructed us on Prayer and how to pray in Matthew the 6th chapter.
Matthew 6:5-15 (NCV)
5 “When you pray, don’t be like the hypocrites. They love to stand in the synagogues and on the street corners and pray so people will see them. I tell you the truth, they already have their full reward.
6 When you pray, you should go into your room and close the door and pray to your Father who cannot be seen. Your Father can see what is done in secret, and he will reward you.
7 “And when you pray, don’t be like those people who don’t know God. They continue saying things that mean nothing, thinking that God will hear them because of their many words.
8 Don’t be like them, because your Father knows the things you need before you ask him.
9 So when you pray, you should pray like this: ’Our Father in heaven, may your name always be kept holy. 10 May your kingdom come and what you want be done, here on earth as it is in heaven. 11 Give us the food we need for each day. 12 Forgive us for our sins, just as we have forgiven those who sinned against us. 13 And do not cause us to be tempted, but save us from the Evil One.’
14 Yes, if you forgive others for their sins, your Father in heaven will also forgive you for your sins.
15 But if you don’t forgive others, your Father in heaven will not forgive your sins.
The latter part of this section informs us that our own lives and the way we live them can affect our prayer lives and ability to pray unto God. Our own sins can affect our ability to pray and have dialog with God. It is only though God's Holy Spirit that a Christian or mere human can approach God to ask anything and it is God's Holy Spirit that intercedes on our behalf all without us being conscience of it happening. The Christian an ask for others to pray for them or with them but ultimately it is God's own gift, His Holy Spirit that enables the individual Christian to bring our needs, desires, and request, directly to God, Himself.
Romans 8:26-27 (NCV)
26 Also, the Spirit helps us with our weakness. We do not know how to pray as we should. But the Spirit himself speaks to God for us, even begs God for us with deep feelings that words cannot explain.
27 God can see what is in people’s hearts. And he knows what is in the mind of the Spirit, because the Spirit speaks to God for his people in the way God wants.