This is what I never understood. It seems extremely egotistical to pray and tell God what he should do. If God is all knowing and all powerful, then he will do what is best regardless. Is he going to have a master plan that requires one thing to happen, then change his mind because some idiot prayed about it?
It seems like the most appropriate prayers are "Let thy will be done" or asking for wisdom. I agree, asking for a specific thing just seems wrong (although I do ask for help when I lose my car keys!)
I do seem to recall -- from 'way back in the days when I was getting religious instruction -- that God would, indeed, grant requests made in prayer. There was a trick to it, though, and that was to get the wording exaaaaactly right. He seemed to be fond of granting what the mark was praying for, but with an unpleasant twist. Kinda like, "Okay, you prayed that Uncle Harry wouldn't die, so I'll grant the request ... so he'll be in a coma for ten years."
This was taught to us by way of getting us not to pray that way, but it did make it seem that God acted like the Marx Brothers. With a really twisted sense of humor.