The third day of Diwali is considered to be the most important day. It is known as the day of the Lakshmi Puja. Goddess Lakshmi is the Goddess of wealth and prosperity and it is believed that she roams around people’s homes during Diwali. Hence, the Lakshmi Puja is performed to please Goddess Lakshmi so that she can bless the family with prosperity and well-being for the whole year. 
People also take the effort to keep their house clean during Diwali, as it is believed that the Goddess visits the cleaner houses first. Rangolis are drawn at the entrances of houses to entice Goddess Lakshmi and welcome her into their home when she visits. The puja is performed in the evening during pradosh kaal which is considered to be auspicious. 
Handfuls of grains are sprayed in the center of a cloth and a kalasha made of gold, silver or copper is placed on it. Three-quarters of the kalasha is filled with water and betel nut, a flower, a coin, and some rice grains are added to it. Five kinds of leaves are arranged. A small dish filled with rice grains is placed on a kalasha. The idol of Goddess Lakshmi is placed on top of the kalasha and a lotus is drawn over the rice grains with turmeric powder and coins are placed around the idol.
The idol of Goddess Lakshmi is placed in a plate and is bathed with water, panchamrita (a mixture of milk, curd, ghee or clarified butter, honey, and sugar) and then with water containing a gold ornament or a pearl. The idol is cleaned and placed back on the kalasha. Alternately, flowers, water and panchamrita are sprinkled on the idol.
Offerings such as sandalwood paste, a garland of cotton beads, saffron paste, ittar {perfume}, turmeric, kumkum, abir, and gulal are made to the Goddess. Puffed rice and batasha (varieties of Indian sweets) are also placed near the idol. Then puffed rice, batasha, coriander seeds, and cumin seeds are poured over the idol. Lines similar to the Swastika are made on the safe in which the worshipper keeps their valuables and it is worshiped as a symbol of Lord Kubera. Finally the puja is concluded with an Aarti in honour of Goddess Lakshmi.

To know more about Diwali and the pujas to be performed during Diwali, click here.