Extracts from the Writings of Shoghi Effendi
The simplicity characterizing the offering of Bahá’í prayers, whether obligatory or otherwise, should be maintained. Rigidity and rituals should be strictly avoided.
(In the handwriting of Shoghi Effendi, appended to a letter dated 30 October 1936 written on his behalf to an individual believer) 
Extracts from Letters Written on Behalf of Shoghi Effendi
The Guardian wishes you, therefore, to pray, and to supplicate the Almighty that He may give you a fuller measure of His grace; that through it your spiritual energies may be quickened and that you may become more imbued with that spirit which must needs animate, sustain and strengthen every sincere and true follower of the Faith.
Concerning the directions given by Bahá’u’lláh for the recital of certain prayers, Shoghi Effendi wishes me to inform you that these regulations—which by the way are very few and simple—are of a great spiritual help to the individual believer, in that they help him to fully concentrate when praying and meditating. Their significance is thus purely spiritual.
In prayer the believers can turn their consciousness toward the Shrine of Bahá’u’lláh, provided that in doing so they have a clear and correct understanding of His station as a Manifestation of God.
With regard to your spiritual experiences, the Guardian has been very interested to share them. He would, however, urge you to always use and read, during your hours of meditation and prayer, the words revealed by Bahá’u’lláh and the Master.
The problem with which you are faced is one which concerns and seriously puzzles many of our present-day youth. How to attain spirituality is, indeed, a question to which every young man and woman must sooner or later try to find a satisfactory answer. It is precisely because no such satisfactory reply has been given or found, that modern youth finds itself bewildered, and is being consequently carried away by the materialistic forces that are so powerfully undermining the foundation of man’s moral and spiritual life.
Indeed, the chief reason for the evils now rampant in society is a lack of spirituality. The materialistic civilization of our age has so much absorbed the energy and interest of mankind, that people in general no longer feel the necessity of raising themselves above the forces and conditions of their daily material existence. There is not sufficient demand for things that we should call spiritual to differentiate them from the needs and requirements of our physical existence. The universal crisis affecting mankind is, therefore, essentially spiritual in its causes. The spirit of the age, taken on the whole, is irreligious. Man’s outlook upon life is too crude and materialistic to enable him to elevate himself into the higher realms of the spirit.
It is this condition, so sadly morbid, into which society has fallen, that religion seeks to improve and transform. For the core of religious faith is that mystic feeling that unites man with God. This state of spiritual communion can be brought about and maintained by means of meditation and prayer. And this is the reason why Bahá’u’lláh has so much stressed the importance of worship. It is not sufficient for a believer to merely accept and observe the teachings. He should, in addition, cultivate the sense of spirituality, which he can acquire chiefly by the means of prayer. The Bahá’í Faith, like all other Divine religions, is thus fundamentally mystic in character. Its chief goal is the development of the individual and society, through the acquisition of spiritual virtues and powers. It is the soul of man that has first to be fed. And this spiritual nourishment prayer can best provide. Laws and institutions, as viewed by Bahá’u’lláh, can become really effective only when our inner spiritual life has been perfected and transformed. Otherwise religion will degenerate into a mere organization, and become a dead thing.
The believers, particularly the young ones, should therefore fully realize the necessity of praying. For prayer is absolutely indispensable to their inner spiritual development, and this, already stated, is the very foundation and purpose of the Religion of God.
(8 December 1935 to an individual believer, published in “Bahá’í News” 102 (August 1936), p. 3) 
...the obligatory prayers are by their very nature of greater effectiveness and are endowed with a greater power than the non-obligatory ones, and as such are essential.
While praying it would be better to turn one’s thoughts to the Manifestation as He continues, in the other world, to be our means of contact with the Almighty. We can, however, pray directly to God Himself.
(27 April 1937 to the National Spiritual Assembly of India and Burma) 
You have asked whether our prayers go beyond Bahá’u’lláh: it all depends whether we pray to Him directly or through Him to God. We may do both, and also can pray directly to God, but our prayers would certainly be more effective and illuminating if they are addressed to Him through His Manifestation, Bahá’u’lláh.
The Guardian wishes me to assure you that he sees no objection to the friends coming together for meditation and prayer. Such a communion helps in fostering fellowship among the believers, and as such is highly commendable.
[...] was a matter of deepest [...] to the Guardian to hear of the news of the formation in Honolulu of a Morning Class of prayer and meditation conducted by dear Mrs. ... in her home, inasmuch as he feels the absolute necessity for the friends to make now a special effort to cultivate the devotional side of their Bahá’í life in preparation for a more intensified and successful service, particularly in the teaching field.
(1 May 1938 to an individual believer and a Local Spiritual Assembly) 
Although you seem to feel that your prayers have not so far been answered, and do no longer have any hope that your material conditions will ameliorate, the Guardian wishes you nevertheless not to allow such disappointments to undermine your faith in the power of prayer, but rather to continue entreating the Almighty to enable you to discover the great wisdom which may be hidden behind all these sufferings. For are not our sufferings often blessings in disguise, through which God wishes to test the sincerity and depth of our faith, and thereby make us firmer in His Cause?
The true worshipper, while praying, should endeavour not so much to ask God to fulfil his wishes and desires, but rather to adjust these and make them conform to the Divine Will. Only through such an attitude can one derive that feeling of inner peace and contentment which the power of prayer alone can confer.
You should rest assured that your strict adherence to the laws and observances enjoined by Bahá’u’lláh is the one power that can effectively guide and enable you to overcome the tests and trials of your life, and help you to continually grow and develop spiritually.
The Guardian particularly appreciates the fact that you have been faithfully observing Bahá’u’lláh’s injunction regarding the recital of the daily obligatory prayers, and have thereby set such a high example before your Bahá’í fellow-youth. These daily prayers have been endowed with a special potency which only those who regularly recite them can adequately appreciate. The friends should therefore endeavour to make daily use of these prayers, whatever the peculiar circumstances and conditions of their life.
He wishes again to assure you he will pray for your spiritual advancement in the Holy Shrines. The power of God can entirely transmute our characters and make of us beings entirely unlike our previous selves. Through prayer and supplication, obedience to the divine laws Bahá’u’lláh has revealed, and ever-increasing service to His Faith, we can change ourselves.
There are no set forms of meditation prescribed in the teachings, no plan, as such, for inner development. The friends are urged—nay enjoined—to pray, and they also should meditate, but the manner of doing the latter is left entirely to the individual.
The inspiration received through meditation is of a nature that one cannot measure or determine. God can inspire into our minds things that we had no previous knowledge of, if He desires to do so.
Prayer and meditation are very important factors in deepening the spiritual life of the individual, but with them must go also action and example, as these are the tangible results of the former. Both are essential.
The believers, as we all know, should endeavour to set such an example in their personal lives and conduct that others will feel impelled to embrace a Faith which reforms human character. However, unfortunately, not everyone achieves easily and rapidly the victory over self. What every believer, new or old, should realize is that the Cause has the spiritual power to re-create us if we make the effort to let that power influence us, and the greatest help in this respect is prayer. We must supplicate Bahá’u’lláh to assist us to overcome the failings in our own characters, and also exert our own will-power in mastering ourselves.
Through meditation the doors of deeper knowledge and inspiration may be opened. Naturally, if one meditates as a Bahá’í he is connected with the Source; if a man believing in God meditates he is tuning in to the power and mercy of God; but we cannot say that any inspiration which a person, not knowing Bahá’u’lláh, or not believing in God, receives is merely from his own ego. Meditation is very important, and the Guardian sees no reason why the friends should not be taught to meditate, but they should guard against superstitious or foolish ideas creeping into it.
He feels more emphasis should be laid on the importance and power of prayer, including the use of The Greatest Name, but not over-emphasizing it. It is the spirit behind the words which is really important.
In regard to your question: we must not be rigid about praying; there is not a set of rules governing it; the main thing is we must start out with the right concept of God, the Manifestation, the Master, the Guardian—we can turn, in thought, to any one of them when we pray. For instance you can ask Bahá’u’lláh for something, or, thinking of Him, ask God for it. The same is true of the Master or the Guardian. You can turn in thought to either of them and then ask their intercession, or pray direct to God. As long as you don’t confuse their stations, and make them all equal, it does not matter much how you orient your thoughts.
He is delighted to hear you are now fully recovered and again active in your important work for the Cause. However, you should not neglect your health, but consider it the means which enables you to serve. It—the body—is like a horse which carries the personality and spirit, and as such should be well cared for so it can do its work! You should certainly safeguard your nerves, and force yourself to take time, and not only for prayer and meditation, but for real rest and relaxation. We don’t have to pray and meditate for hours in order to be spiritual.
I might add that he does not believe any radiations of thought or healing, from any group, are going to bring peace. Prayer, no doubt, will help the world, but what it needs is to accept Bahá’u’lláh’s system so as to build up the World Order on a new foundation, a divine foundation!
If you find you need to visualize someone when you pray, think of the Master. Through Him you can address Bahá’u’lláh. Gradually try to think of the qualities of the Manifestation, and in that way a mental form will fade out, for after all the body is not the thing, His Spirit is there and is the essential, everlasting element.
He would advise you to only use the short midday Obligatory Prayer. This has no genuflections and only requires that when saying it the believer turn his face towards ‘Akká where Bahá’u’lláh is buried. This is a physical symbol of an inner reality, just as the plant stretches out to the sunlight—from which it receives life and growth—so we turn our hearts to the Manifestation of God, Bahá’u’lláh, when we pray; and we turn our faces, during this short prayer, to where His dust lies on this earth as a symbol of the inner act.
Bahá’u’lláh has reduced all ritual and form to an absolute minimum in His Faith. The few forms that there are—like those associated with the two longer obligatory daily prayers—are only symbols of the inner attitude. There is a wisdom in them, and a great blessing, but we cannot force ourselves to understand or feel these things, that is why He gave us also the very short and simple prayer, for those who did not feel the desire to perform the acts associated with the other two.
He suggests that you daily pray to Bahá’u’lláh to let you meet a soul receptive to His Message. The power of prayer is very great, and attracts the Divine confirmations. He, also, will pray for your teaching work there.
He thinks it would be wiser for the Bahá’ís to use the Meditations given by Bahá’u’lláh, and not any set form of meditation recommended by someone else; but the believers must be left free in these details and allowed to have personal latitude in finding their own level of communion with God.