Among believers who pray to angels are some Jews, Catholics, Orthodox Christians, astrologists, Sikhs, Hindus, some Buddhists, and people who follow New Age spirituality.
Believers who don't pray to angels include some Jews, Protestant Christians, Muslims, Mormons, and some Buddhists.
In Judaism, some Orthodox and Conservative congregations sing prayers to angels as part of their Sabbath services. One of those prayers, the Shalom Aleichem, welcomes angels to the worship service in the synagogue. Jews may also sing the Shalom Aleichem prayer before eating their weekly Sabbath meal. The Shalom Aleichem begins: "We wish you peace, attending angels, angels of the most sublime, the King of kings, the Holy One praised be He." Some Jews recite a bedtime prayer that invokes four archangels to protect them while they're sleeping: "In the name of HASHEM, God of Israel, may Michael be at my right, Gabriel at my left, Uriel before me, and Raphael behind me; and above my head the Shekhina [the female presence of God]." Reform congregations don't tend to pray to angels.
In Christianity, Catholics and Orthodox Christians often pray to archangels and their individual guardian angels. Catholics point to Tobit 12:1 from the Catholic Bible (in which the archangel Raphael tells two people that he offered their prayers to God) to support their belief that it's acceptable to ask angels to intercede before God with people's prayers. A famous Catholic guardian angel prayer is: "Angel of God, my Guardian dear, to whom His love commits me here, ever this day (or night) be at my side, to light and guard, to rule and guide. Amen." Orthodox Christians may pray this Orthodox prayer to their guardian angels: "Oh angel of God, my holy guardian, given to me from heaven, enlighten me this day, and save me from all evil. Instruct me in doing good deeds, and set me on the path of salvation. Amen." However, Protestant Christians and Mormons believe that people should pray directly to God and not go through angels. They may cite 1 Timothy 2:5 of the Protestant Bible: "For there is one God and one mediator between God and men, the man Christ Jesus."
In astrology, believers may pray directly to angels who emanate 72 different kinds of divine energies, all of which correspond with parts of astrology, since as planets, zodiacal signs, or specific times. Three angels in particular (the Incarnation Angel, the Heart Angel and the Intellect Angel), are different for each person, depending on the date and time of that person's birth. People who practice astrology believe that their prayers will be most powerful if they pray mostly to those three angels, who influence their lives the most.
In Islam, praying to angels or anyone besides God himself is considered to be a major sin, called "shirk," which means treating someone (such as an angel) as if he or she is God's partner. The Qur'an forbids that in chapter 7 (Al A'raf), verses 192-194: "Do they indeed ascribe to Him as partners things that can create nothing, but are themselves created? No aid can they give them, nor can they aid themselves!"
In Sikhism, people may pray to angels as part of their process of uniting their souls more deeply with the divine, which is everywhere. Sikhs may either say prayers or meditate, and they believe that if they meditate on God's name deeply enough, they may be changed into angelic beings themselves. The Sikh holy scripture Sri Guru Granth Sahib says on page 90, line 17: "They are transformed from humans into angels, meditating on the Naam, the Name of the Lord."
In Hinduism, believers may pray to angelic beings called devas who can give them specific types of blessings, according to what they need. Sometimes, Hindus use icons of devas (often statues of them) to help them concentrate on their prayers.
In Buddhism, some believers (especially Mahayana Buddhists) meditate to angelic beings called bodhisattvas, often asking the bodhisattvas to help them overcome their suffering on Earth. However, Buddhists usually only meditate, rather than pray.
In New Age spirituality, believers pray directly to angels often to seek blessings for various parts of their lives, from their relationships to their finances. New Age spirituality emphasizes connecting with what believers see as the divine part of themselves to become receptive to communicating with angels through prayer. People who follow New Age spirituality may either invoke specific angels for help with specific needs, or pray generally to any angel who represents an aspect of God's love.