Gayatri mantra is Hinduism's most representative prayer. Many hindus recite it on a daily basis, not only contemplating its straightforward meaning, but also dwelling on and imbibing its sound, regarded to be pregnant with spiritual meaning. For this reason nearly all hindu prayers and mantras are sung. The gayatri was first recorded in the Rig Veda (iii, 62, 10) which was composed in Sanskrit about 2500 to 3500 years ago, and by some reports, the mantra may have been chanted for many generations before that.
Prayer is achieved through pooja (worship) done either at the family shrine or a local temple. We can see from Krishna's injunction that prayer is fundamental to hinduism, that to dwell constantly on god is key to enlightenment. Prayer repetition (through mantras) using maalaas (Hindu prayer beads) are a strong part of Hinduism.
Some other extremely popular deities are Krishna and Rama (incarnations of Vishnu), Ma Kali (Mother kali, the feminine deity, or Mother Goddess, aka Durga, Parvati, shakti, etc.) and Ganesha (the famous elephant-headed god of wisdom). It is epitomised by the devotion of the God Hanuman or Bajrang Bali for his Lord Rama. Another major form of prayer for hindus involves a heavy focus on meditation, through Hindu yoga that stills the mind in order to focus on God.