This is from a recent Q&A from his web site Reasonable Faith.

Here’s the question:

My question is this: what is the point of prayer? Here prayer is defined as an attempt to communicate with God.

God either can read our thoughts or he cannot. If he can read our thoughts, there is surely no need to try to transmit or broadcast them to him as he already knows what they are. If he cannot read our thoughts, then any thought-based effort to contact him is futile. It doesn’t matter what type of prayer it is (eg petition, thanksgiving, repentance), there is no point in making any effort to send it up to him.

Of course, Christianity generally holds that God is omniscient and therefore able to read our thoughts, so the first of these scenarios would be the applicable one. The characteristic of omniscience makes the concept of prayer all the more redundant as it means God already knows any information that might be communicated to him, and exactly what the best thing is to do about it, so prayer could not in any way influence his decisions.

I am well aware that the Bible commands us to pray in numerous instances, but in the light of this argument this strikes me as an incredibly arbitrary thing for a good God to command, and thus makes the reliability of the Bible all the more questionable to me.

Currently it seems to me that the idea of prayer is most sensibly explained as an addictive placebo that gives people a greater sense of control over their circumstances than they actually have.

Dr. Craig’s response is long, but here is the key part:

Yes, God can read our thoughts. So how is that problematic for the spiritual discipline of prayer? You say, “there is surely no need to try to transmit or broadcast them to him as he already knows what they are.” Hold on, Joe! Seriously, do you think prayer is a matter of providing God information? You defined prayer as communication with God. You don’t communicate with another person through a third-person relationship. You enter into what has been called an “I-thou” relationship. You speak to another person, not just about that person. Your girlfriend or wife would be decidedly unimpressed if you rationalized never telling her “I love you” on the grounds that she already knows that! Anybody that obtuse is on his way to a break-up! Two people who are in love with each other want to speak to each other, to build an intimate relationship with each other.

So, sure, God reads my mind, and that enables me to pray to Him at any moment, even when audible prayers would be inappropriate. I can shoot up a thought-prayer, “Thank you, Lord!” or “God, give me wisdom!” at a moment’s notice. This is what people in a relationship do. Can you imagine anyone so obtuse as to say, “I don’t have to thank John for what he did for me because he already knows I’m grateful”? Or “I don’t have to apologize to Susan because she already knows I’m sorry”?

Moreover, did it not occur to you that such personal communication may be good for you? I-thou relationships open you up as a person, to make you a more loving, transparent, and vulnerable person. Prayer to God is the same way. God knows what is good for us and so wants us to talk to Him.

But in addition to that – yes, God can answer prayers:

You have a second, different objection to prayer: “omniscience makes the concept of prayer all the more redundant as it means God already knows any information that might be communicated to him, and exactly what the best thing is to do about it, so prayer could not in any way influence his decisions.” This is an objection to the efficacy of prayer. What the objection overlooks is that God can take prayers (or the lack thereof) into account in His providential planning of the world. Knowing that Joe would freely pray in a certain set of circumstances, God may actualize a world in which Joe’s prayers are answered; but had God known that Joe would not pray, God may have actualized something else instead. Prayers, then, are not an effort to change God’s mind. Rather God takes account of prayers in choosing which world to actualize. Prayers thus make a counterfactual difference: if I were not to pray, then something else would have been the case instead. Knowledge of this sort is called “middle knowledge,” and there’s a lot on this website about this fascinating topic.

I have to tell you that in a poll of some of my male apologist friends, we all struggle with prayer. I can’t say why they struggle with prayer, but in my case it’s just that I have trouble understanding how big God is and how much more he can do – especially when there are so many problems and I can’t work on them all myself. My personality is very practical. If something needs to be done, I do it. If something needs to be said, I say it. The best thing to do when any dragon appears is to attack it. The best thing to do when a princess is in distress is to rescue her. I do not call for help when there is anything for me to do. Prayer is like a last resort!

Having said that, I do understand that God wants to partner with me and that means that my perception of him changes as I work my way through the standard prayer practices… acknowledging who God is, thanking him for what I have, asking him for what I need, asking him to defend himself and act to make people aware of him and his character, etc. I do struggle with it, though. It’s not as easy for me to do as go to church or read the Bible. Apologetics, of course, is no problem for me! I wish someone would encourage me to pray.

I think the middle knowledge point he raised is key, though – God, prior to creating the world can factor in all of your prayers that you freely pray, because he foreknows everything you will do in the circumstances (time and place) that he places you in. So, have confidence. Even if he doesn’t answer you the way you expect, your prayers were heard.

Aside from all that, I do think that God is pleased when I pray about my concerns to him. It shows him how I am changing, and have his priorities in my mind, and not my own. If you are interested in pleasing God, then talking to him about your concerns and priorities is a good thing to do, especially as your concerns and priorities become more like his.