Doing puja to Lord Krishna is a very good practice to develop Universal Knowledge and love, to control and discipline the mind, as He is considered a manifest form of God, or avatar. In the Hindu religion, He is considered an avatar or Lord Vishnu, (the maintainer of Universe) and is related with Jainism's tirthankaras and is regarded as an enlightened being in Buddhism.
Krishna puja vidhi for Janmashtami is an essential ritual that takes place on midnight of day of birth of Lord Krishna, i.e. Bhadrapada Krishna Paksha 8th day (according to Hindu calanader). (कृष्ण पूजा विधि भगवान् श्री कृष्ण के जन्मदिन (भाद्रपद कृष्ण अष्टमी तिथि) पर आधी रात को किया जाने वाला परम आवश्यक अनुष्ठान है.)
This easy Baby Krishna puja vidhi can be performed quickly on Janmashtami with bliss. (इस सरल कृष्ण पूजा विधि की सहायता से जन्माष्टमी पर भगवान् कृष्ण की पूजा बड़े आनंद के साथ शीघ्रता से कर सकते हैं.)
Take a bath before performing the puja and mark your forehead with ashtagandha (sandalwood) or gopi chandan (mud of Vrindavan).
In a clean quiet table, place a white cotton cloth and put it there. You need to put a Lord Krishna statue or image in the center of the altar in a large deep container. Arrange a puja plate with water to sprinkle, kumkum, sandalwood, incense, aarti lamp and flowers and put it at the side.
Arrange another plate with saatvik fruit, water to drink and more flowers. Make a ghee or sesame oil diya (lamp) and place it there, without burning it.
When all is set up, you take a spoon with left hand, put water on your right hand and say "Om achyutaya namaha" and drink it quietly. Take more water and say "Om anantaya namaha" and drink. Last mantra "Om Govindaya namaha" and drink, then put water on both hands and dry it.
Chant the brahma samhita Govindam adi purusham while you bathe the idol with milk, ghee, orange juice, flowers and simple water. Dry the murti (statue) and put that bowl at side on other table. Place the food, flowers, water and ghee diya next to it after abhishekam (the bath)
Put sandalwood on lord Krishna's idol. Begin chanting the prayer shubham karoti kalyanam and light the diya. Then say gurur brahma gurur vishnu.... then, you chant any Krishna bhajan that you like and offer an incense stick 7 times in a circular clockwise motion. Then the arti lamp with 1 or 5 wicks, and then offer the chamara wisk to scare flies, so that Lord would be comfortable.
Put a little kumkum at Lord Krishna's feet and then to your forehead and devotees around. Blow the conch shell and ask forgiveness for doing wrong or forgetting something during puja. You can leave there the offerings of fruits, water, flowers and rice and later eat them and use them (never waste it or throw it) or you can say namaskar to Lord and distribute to the devotees, saying jai mahaprasada or jai jinendra.
You can do japa meditation with "Hare krishna" or OM NAMO BHAGAVATE VASUDEVAYA after puja.