"With all prayer and petition pray at all times in the Spirit,"
When we walk with Jesus, we walk in the knowledge that His spirit lives within us and His spirit is constantly speaking to our spirit. If we are listening we will know how to pray. For He will bring to mind those things we ought to pray about. "In the Spirit; for true prayer is spiritual, and it is not true prayer unless by the Holy Spirit the heart is filled with heavenward longings and aspirations, changing our prayer from cold form to heartfelt realities. The ordinary habit of the soul should be prayerful, realizing the presence of God and looking for his grace and guidance. And watching thereunto; that is, 'towards' spirituality, against formality, as also against forgetfulness and neglect of prayer. Perhaps also the idea of watching for the answer is involved, as you wait for an answer when you have dispatched a letter." (The Pulpit Commentary: New Testament; Old Testament; Ages Software)