I was talking with someone who said that they pray in tongues for everything. When we pray "in the spirit", all the limits of our language are gone. Why should we pray only in our limited "known language"?
Pray in your "tongues" language and then pray for understanding. A lot of times when you pray in tongues only, you don't know what you are praying because your mind doesn't understand what you are praying.
I've asked God what I'm praying for in tongues. Sometimes He will tell me, "It's none of your business." Sometimes He will tell me what I'm praying about. Your mind has to have your spirit man tell you, or the Holy Spirit Himself will tell you what you're praying. This goes along with His Presence.
When we are praying in the spirit, His Presence will be trying to manifest. Many times we will shift gears doing this ... shifting from the natural thinking of the world we live in to the spiritual side. The Holy Spirit will take us and we'll suddenly realize that we are thinking more spiritually-minded than we are in the natural. This is what we want.
Reverend Robert W. & Mary C. Butler