While we are admonished to make our requests known and pray for one another there are times when for one reason or another we are not free to share the details. Perhaps the request involves other people who would not appreciate the details being made public. Perhaps the situation is a sensitive and/or private matter which we do not feel that we can disclose to anyone other than close family or friends. Sometimes we do not even feel that it is appropriate for us to share with them.
Sometimes sharing the request could result in gossip, cast someone else in a negative light, etc. We may be reluctant to do that and yet the need lies so heavy on our heart that we cry out for others to please pray! Sometimes the person themselves does not even know what is wrong. They are just seized with an urgency to pray and ask others to pray as well.
While it definitely is helpful to know the details of what we are praying about, is it possible to effectively pray without knowing the details? Yes, I believe it is. You see, while we may not know the details or we may not even know who or what we are praying about, the Holy Spirit does. We may not know the words to say but I believe that if we ask Him to help us, to give us the words we need... He will do so.
Over the years, I have had people stunned as I have begun to pray about exactly what they needed. They knew full well that I knew nothing of the details and yet the words I was praying was exactly what they needed to hear. I've had people sob in my arms as they realized that it had to be the Holy Spirit praying through me, or someone else and it confirmed for them that God truly was aware of their need and... He cared.
When we feel the urge to pray whether for ourselves or others and do not know how to pray, let us ask God to help us pray. He will.