When you go alone in the quiet time and place with the Book quietly pray: "blessed Prayer-Spirit, Master-Spirit, teach me how to pray," and He will. Do not be nervous, or agitated, wondering if you will understand. Study to be quiet; mind quiet, body quiet. Be still and listen. Remember Luther's version of David's words, "Be silent to God, and let Him mould thee."
You will find your praying changing. You will talk more simply, like a man transacting business or a child asking, though of course with a reverence and a deepness of feeling not in those things. You will quit asking for some things. Some of the old forms of prayer will drop from your lips likely enough. You will use fewer words, maybe, but they will be spoken with a quiet absolute faith that this thing you are asking is being worked out.
This thing of letting the Spirit teach must come first in one's praying, and remain to the last, and continue all along as the leading dominant factor. He is a Spirit of prayer peculiarly. The highest law of the Christian life is obedience to the leading of the Holy Spirit. There needs to be a cultivated judgment in reading His leading, and not mistaking our haphazard thoughts as His voice. He should be allowed to teach us how to pray and more, to dominate our praying. The whole range and intensity of the spirit conflict is under His eye. He is God's General on the field of action. There come crises in the battle when the turn of the tide wavers. He knows when a bit of special praying is needed to turn the tide and bring victory. So there needs to be special seasons of persistent prayer, a continuing until victory is assured. Obey His promptings. Sometimes there comes an impulse to pray, or to ask another to pray. And we think, "Why, I have just been praying," or, "he does pray about this anyway. It is not necessary to pray again. I do not just like to suggest it." Better obey the impulse quietly, with fewest words of explanation to the other one concerned, or no words beyond simply the request.
Let Him, this wondrous Holy Spirit teach you how to pray. It will take time. You may be a bit set in your way, but if you will just yield and patiently wait, He will teach what to pray, suggest definite things, and often the very language of prayer.
You will notice that the chief purpose of these four suggestions is to learn God's will. The quiet place, the quiet time, the Book, the Spirit -- this is the schoolroom as Andrew Murray would finely put it. Here we learn His will. Learning that makes one eager to have it done, and breathes anew the longing prayer that it may be done.
There is a fine word much used in the Psalms, and in Isaiah for this sort of thing -- waiting. Over and over again that is the word used for that contact with God which reveals to us His will, and imparts to us anew His desires. It is a word full of richest and deepest meaning. Waiting is not an occasional nor a hurried thing. It means steadfastness, that is holding on; patience, that is holding back; expectancy, that is holding the face up to see; obedience, that is holding one's self in readiness to go or do; it means listening, that is holding quiet and still so as to hear.