The best prayer is to keep all your thoughts, words and actions consistently towards the goal of your prayers. These three actions have spiritual components and heaven responds to your deepest thought, word and action.
Remember when Jesus asked Peter to walk on water, at some point Peter doubted. That doubt was the deepest thought. That doubt was answered as he fell into the water. Actually Peter's prayer was answered.
When your deepest thought is so pure, that thought and the following actions if any, will be answered. Such faith is so rare, that only few men have. They include Jesus and Buddha. People saw their miracles and flock to them for healing.
Now if you do this prayer with others, the prayer will be even more powerful. That is why it is written "When two or more is gathered in my name..." .
So be careful of asking God for something and doubting about it.
Your doubt in which you have more faith, will actually override you formal prayer request. This is why many feel that their prayers are not answered. The trouble is that heaven know your deepest thought more than you know.