I pray for God's will to be done. I pray to think of others. I pray for my own spirit to realize there is more to life than myself. I do understand that God's will will be done regardless. It doesn't matter how much everyone prays about a particular thing.
Think about Schivao for instance.. many prayed for her to live... she did not. The purpose of prayer isn't to get what you want.. it's to put yourself at God's mercy.
Except for that wedding at Cana. And Moses over there on Sinai...