How do people in same religion pray differently?

The Hindu uses many different forms of prayer in their devotions to God.

Throughout the millennia the Hindu yogis experimented and practiced the ancient science of prayer gradually evolving it into different techniques so as to be more useable to the general masses.

Bhajans are simple songs or chants to the God that when applied correctly bring about great changes in the devotee. Vibrations from devotional singing can lead one into attunement with the Cosmic Vibration and even bring on deep mystic states such as Samadhi.

In Bhajan, the devotee chooses a spiritualized song ie, a song with deep spiritual meaning, infused with love and devotional prose generally by a saint who has used that song or chant to receive actual response from God.

Those who want the best results from bhajans should chant them alone or with true devotees of God with deep attention, spiritual fervor, conviction, love and enthusiasm.

Examples or soul-saturated songs and how to sing them correctly can be found in the teachings of Swami Sivananda, Paramahansa Yogananda and other great saints of the Hindu tradition.

The best book I have come across so far on Bhajan (Singing-Soul Prayer) is called Cosmic Chants by Paramahansa Yoganandapublished by the Self-Realization Fellowship.

Bhajan is wonderful part of the Hindu tradition and helps the devotee in developing Bhakti (Love through devotion).

Mantra is an advanced form of prayer.

A mantra is carefully chosen or received by a guru and chanted either out loud, as a whisper or silently. According to the law of mantra any mantra intoned correctly out loud has its effects upon the physical - a mantra chanted as a whisper so that even a person sitting in front of you would not be able to hear it has its effects upon the mental realm and any mantra intoned silently ie mentally in the correct manner has its effects upon the psychic and spiritual planes.

A mantra consists of a Word or several Words from the Sanskrit language which have certain sound vibrations which help the devotee attune his consciousness to higher planes as well as invoke specific subtle energies into and around the aura, making it more dynamic and capable of expressing higher aspects of Cosmic Truth ie, love, wisdom, joy etc

Some great info on Mantra and its practice include:

Meditation and Mantras by swami vishnu-devananda

Essence of Yoga by Sri Swami Satchidananda

The A-U-M cassette by the Aetherius Society

Initiation into Dynamic and Soul Mantra by the Aetherius Society

Realize you Inner potential by Richard Lawrence & Sir George King.

In addition to Bhajan and Mantra the yogi uses what might be regarded as: Spiritual Prayer or Dynamic Prayer in their devotions.

In Dynamic Prayer (yogic prayer) the Hindu uses his knowledge of the subtle manipulation of energies, correct techniques and guru-given instructions to make his prayers scientific.

There are many slightly different techniques in prayer, some more effective than others.

Its up to the prayer as to what technique he or she wishes to adopt according to the tradition one belongs and type of spiritual practice or even belief one has.

I would study the following books on the correct techniques of prayer based by the great Hindu proponent and spiritual teacher Paramahansa Yogananda, entitled:

Journey to Self-realization

Whispers from Eternity

In the Sanctuary of the Soul: A guide to Effective Prayer

How you can talk with God

Metaphysical Meditations

Scientific Healing Affirmations

to name a few!!!