I lead a ministry called GriefShare that helps people who have lost a loved one. We had our first session of the semester last night. At the end of the class, after people had shared who they had lost and the intense hurt, pain and sorrow that was there, I didn't know how to to pray. I didn't know what to say.
So I thanked God that he knows how to pray and what to pray when I don't. We are told in Romans 8:26 that "We do not know what we ought to pray for, but the Spirit himself intercedes for us with groans that words cannot express." Just a few lines later, in verse 34 we are told that Jesus himself is at the right hand of God and is also interceding for us.
So if there is ever a situation where you do not know how to pray or what to pray just ask Jesus to do the praying for you through the Spirit. Afterall, Jesus was pretty good at it while he walked on this earth and promised us the Holy Spirit to be His presence with us once He was no longer physically present.