There is much misunderstanding and disagreement about the subject of praying in tongues, and it is most helpful to read 1 Corinthians 14, which deals extensively with the issue of praying in tongues within the Church and also in our own personal prayer life.
It is important to understand what the benefit is of praying in the Spirit in our own personal prayer time with the Lord.
Praying in the Spirit is a vital part of intercession for the Word of God in Romans 8:26,27 says that we do not know how to pray as we ought to, and that by praying in the Spirit, we are allowing the Spirit of God to make intercession for us and through us according to the will of God. There are many times when intercessors wake up during the night and sense a prayer burden, but do not know what to pray for. After praying in the Spirit for a period of time this burden is lifted. There are some instances where God has confirmed to certain intercessors at the precise time when they began to pray in the Spirit that someone was in grave danger or that there were situations that needed to be dealt with where there was breakthrough at the exact time when intercession was being made.
Another purpose of praying in the Spirit in our own devotional prayer time is that when we pray in the Spirit, we are in essence exercising our spirit. This means that we are building up and strengthening ourselves in our spirit by praying in the Holy Spirit.
I do not pray in the Spirit for any set period of time, but probably in any given day, I pray in the Spirit many times.
We should pray with our understanding when we know what we are praying for, and praying the scriptures is the most powerful prayer that we can pray. We need to be in agreement with God's Word.
"What is it then? I will pray with the spirit, and I will pray with the understanding also: I will sing with the spirit, and I will sing with the understanding also." (1 Corinthians 14:15).
"Follow after charity, and desire spiritual gifts, but rather that ye may prophesy.
For he that speaketh in an unknown tongue speaketh not unto men, but unto God: for no man understandeth him; howbeit in the spirit he speaketh mysteries.
But he that prophesieth speaketh unto men to edification, and exhortation, and comfort.
He that speaketh in an unknown tongue edifieth himself; but he that prophesieth edifieth the church.
I would that ye all spake with tongues, but rather that ye prophesied: for greater is he that prophesieth than he that speaketh with tongues, except he interpret, that the church may receive edifying.
Now, brethren, if I come unto you speaking with tongues, what shall I profit you, except I shall speak to you either by revelation, or by knowledge, or by prophesying, or by doctrine?
And even things without life giving sound, whether pipe or harp, except they give a distinction in the sounds, how shall it be known what is piped or harped?
For if the trumpet give an uncertain sound, who shall prepare himself to the battle?
So likewise ye, except ye utter by the tongue words easy to be understood, how shall it be known what is spoken? for ye shall speak into the air.
There are, it may be, so many kinds of voices in the world, and none of them is without signification.
Therefore if I know not the meaning of the voice, I shall be unto him that speaketh a barbarian, and he that speaketh shall be a barbarian unto me.
Even so ye, forasmuch as ye are zealous of spiritual gifts, seek that ye may excel to the edifying of the church.
Wherefore let him that speaketh in an unknown tongue pray that he may interpret.
For if I pray in an unknown tongue, my spirit prayeth, but my understanding is unfruitful.
What is it then? I will pray with the spirit, and I will pray with the understanding also: I will sing with the spirit, and I will sing with the understanding also.
Else when thou shalt bless with the spirit, how shall he that occupieth the room of the unlearned say Amen at thy giving of thanks, seeing he understandeth not what thou sayest?
For thou verily givest thanks well, but the other is not edified.
I thank my God, I speak with tongues more than ye all:
Yet in the church I had rather speak five words with my understanding, that by my voice I might teach others also, than ten thousand words in an unknown tongue.
Brethren, be not children in understanding: howbeit in malice be ye children, but in understanding be men.
In the law it is written, With men of other tongues and other lips will I speak unto this people; and yet for all that will they not hear me, saith the Lord.
Wherefore tongues are for a sign, not to them that believe, but to them that believe not: but prophesying serveth not for them that believe not, but for them which believe.
If therefore the whole church be come together into one place, and all speak with tongues, and there come in those that are unlearned, or unbelievers, will they not say that ye are mad?
But if all prophesy, and there come in one that believeth not, or one unlearned, he is convinced of all, he is judged of all:
And thus are the secrets of his heart made manifest; and so falling down on his face he will worship God, and report that God is in you of a truth.
How is it then, brethren? when ye come together, every one of you hath a psalm, hath a doctrine, hath a tongue, hath a revelation, hath an interpretation. Let all things be done unto edifying.
If any man speak in an unknown tongue, let it be by two, or at the most by three, and that by course; and let one interpret.
But if there be no interpreter, let him keep silence in the church; and let him speak to himself, and to God.
Let the prophets speak two or three, and let the other judge.
If any thing be revealed to another that sitteth by, let the first hold his peace.
For ye may all prophesy one by one, that all may learn, and all may be comforted.
And the spirits of the prophets are subject to the prophets.
For God is not the author of confusion, but of peace, as in all churches of the saints." (1 Corinthians 14: 1-33).
(Romans 8:26,27), (Jude 1:20).