God won't answer selfish prayers, and you don't want Him to

A common error that needs to be done away with in any discussion on prayer is to assume God is some kind of genie. With genies, the one rubbing the lamp is the master. What they ask for, they get. It doesn't matter what the wish is, the genie must obey.

With God, it's different. In this relationship, God is the Master. This means He considers both the request, and the motive behind it. When I pray, what am I praying for, and why am I praying for it? Selfish prayers should never be answered. If they are, it's generally so that God can teach us a very valuable lesson. The hard way... But generally speaking, God will not answer a selfish prayer.

Thus, when you pray, consider your motives as much as you consider your desire. Why do you want what you're asking for? If your motives are pure, God may still say no because He has other plans, but you have a much higher chance of a yes. If your motives are purely selfish, you're probably not getting what you ask for, and frankly, you don't want Him to give it to you, because there will be a string or two attached.