Does Prayer Really Change God's Mind?
In R.C. Sproul's new book entitled, "The Prayer of the Lord" he states:

"One of the most frequently asked questions in the theology
of prayer is, “Does prayer change things?” The answer is evident.
The New Testament makes it clear that prayer changes all kinds
of things. We’ll explore that issue more deeply later, but the next
question that comes is, “Does prayer change God’s mind?”
What would induce God to change His mind? Perhaps new
information, some knowledge He lacks until we communicate
it to Him for His consideration. However, the Bible tells us that
when we come to our King in prayer, He already knows what
we are going to ask for and He knows what we need better than
we do. We have to remember that this One we’re talking to is
omniscient. He doesn’t learn anything new. So if you’re going to
change His mind by your prayers, it won’t be because you give
Him new information.
Sometimes we change our minds because we realize that
what we had intended to do was a bad plan, that we made a
mistake in taking such a course. Perhaps we get counsel from
someone who says, “Oh, R. C., you shouldn’t do that because
if you do, A, B, or C is going to follow, and it’s going to mess
everything up.” Is this what happens with God when we come to
Him in prayer? Can we come to Him and say: “God, what You’re planning to do is not good. Let me counsel You to do the right thing”? That would be absurd. God never does anything that is not perfectly good, and we fallen human beings are certainly in no position to counsel Him.
In short, no prayer of any human being ever uttered in his-
tory ever changed the mind of God in the slightest, because His
mind doesn’t ever need to be changed. Sadly, when I say that to
people, they react in horror. They say: “Why should we pray?
What good is prayer if we can’t change God’s mind? Why should
we even engage in this exercise? It’s an exercise in futility.” At that
point, I have to remind them that, as I mentioned above, prayer
does change things, all kinds of things. But the most important
thing it changes is us. As we engage in this communion with
God more deeply and come to know the One with whom we
are speaking more intimately, that growing knowledge of God
reveals to us all the more brilliantly who we are and our need to
change in conformity to Him. Prayer changes us profoundly.
God did not give prayer to the church for His benefit. The
Sovereign has condescended to give us an audience. He has
invited us into the heavenly palace. He has lifted the scepter and
told us to enter. We have access to His very throne. But some-
times we come into His presence far too casually. We come to
Him and say, “Hi, God, how are you doing?” We talk to God
with the kind of familiarity that breeds contempt. It’s a familiar-
ity that reveals we have forgotten who He is and who we are. We
have forgotten that we are peasants in the presence of the King.
Not just a king, but the King, the King of kings, the Lord of
lords, the One who is absolutely sovereign."

I am reminded of Psalm 37:4, "Delight yourself in the LORD, and he will give you the desires of your heart."  May God give us his own desires as we seek Him so that our prayers will be effective!