Worship of Devi is worship of shakti. Shakti means primal energy, ability, capacity, strength. Shakti worship is very ancient and its basis is tantra. It is much more ancient than Islam, Christianity, Judaism, Zoroastrianism, or the Vedic religion. Shakti is inherent in all matter, so it is inherent in us too. In tantra, shakti resides at the root of sushumna, in mooladhara chakra. The shakti is dormant there in each individual. The easiest way to awaken that shakti is by developing the relationship of mother and child. The shakti will awaken through that devotion.
In Shakta tantra there are many systems for worshipping shakti, the primal energy, from which the creator as well as creation has come. The form of God as the Mother existed at the very beginning of creation. Adi Shakti is the original or primal mother. Who can the original creator have been but the mother. It is the mother, not the father, who creates.
We worship the eternal Mother who has no particular form, but is in every form. We should not say that she is formless. She has no particular form, even as clay has no particular form, but every pot is a form of clay. It is her glory we see in the sun and the moon, in all forms of life. We worship the Mother whom yogis know as kundalini shakti, Vaishnavas as Lakshmi, Shaivas as Gauri and Amba, and Christians as Mary.
Over time, the social traditions relegated the Mother to the background. The masculine concept of divinity spread all over the globe and it was widely accepted that God is supreme and nothing is beyond God. There was no thought about the human rights of a female because in most religions the feminine gender was considered to be inferior. But this was not so in the Shakta tradition.
In the Shaiva tradition, Shiva is on the right and Shakti is on the left, but in the Shakta tradition Shakti stands with one leg on Shiva, who sleeps. Moreover, shakti is seen as the sole power in the body at mooladhara chakra. She is the centre or nucleus of all matter. She is also the nucleus within you, not just of your mind, but of your soul.
Shakti worship is performed in various ways, some purely vedic as well as purely tribal. Many indigenous tribes in India and other parts of the world worship a female deity, not strictly according to tantric or vedic rituals, but they still perform ritual worship. The Mother is worshipped among indigenous people everywhere.
In tantric worship, you are dealing with a mysterious, hidden power. Shakti has three forms: benign, destructive and creative. If you awaken her destructive aspect, that is a negative approach, and she will give you a kick. Shakti should be worshipped to awaken her benign powers. You must love and respect your mother. Worship of Devi gives quick rewards, blessings there and then, so rules must be observed. There is a certain grace and dignity in worshipping the Mother Goddess, and one has to respect that. Although there are many methods of worshipping Devi, worship performed with faith and devotion is best.
Systematic methods and procedures are necessary for any action, not just for worship. When the correct procedure is followed, everything follows a specific order and there is no confusion. Vedic rituals may allow some leniency, but this is not the case in the tantric worship of Devi.
Tantra is a pure science of dedication to Matri shakti, mother power. In tantra we behold God as the Mother. You have heard of Ardhanarishwara, the half male, half female God, where the right side is Shiva and the left side is Shakti. In the Chandi Yajna, God is perceived as the mother, the creator, not as the father. She is the ultimate dynamic power. Therefore, in Shakta tantra the Divine Mother is considered to be the first creator, the Adya Shakti. She is the Adi Janani of Brahma, Vishnu and Mahesh, and exists in the heart of all beings.