Lord Krishna's Birthday is celebrated as Krishnashtami or Gokulashtami or Sri Krishna Jayanthi. Both elders and younger generation are very much interested in the celebration. Lord Krishna is the ninth incarnation of Lord Vishnu.
Whenever a new born is available at home, they assume the child as Lord Krishna and thoroughly enjoy the festival. We can see lot of people naming their Boy Child in the name of Lord Krishna (Murali, Anirudhan, Gokul, Gopal, Jagadhish etc;) Even when I was pregnant, my MIL prayed god and when my son was born after Gokulashtami we named him Sanjay Krishnan as per my MIL's wish.
Lord Krishna is reminded for his childhood mischief. So the favorite food that we offer on the day of Krishna Jayanthi includes, Butter, Milk, Curd, Aval, Payasam, Appam, fruits, Betal leaves & Nuts. Also snacks includes Uppu Seedai, Vella Seedai, Kai Murukku etc; If you do not know how to prepare the snacks the most important offering for this occasion are the Milk products mentioned above. Few people also prepare milk kova at home. Nowadays we get the package of snacks in the famous food outlets. History reveals that Lord Krishna's close friend Kuchelar offered him Aval which is Lord Krishna's favorite food. Overwhelmed with joy Lord Krishna offered his friend Kuchelar with wealth and prosperity.
This festival is celebrated in the evening by 6 PM on the Ashtami thidhi during the month of Avani. The Idol of Lord Krishna is decorated with flower garlands or a picture at home. Since this festival falls in the evening, ladies fast till evening and prepare the food for offering. My MIL engage the kids to prepare the seedai balls since it takes time.
In the morning itself, soak some raw rice for Maakolam. By noon we used to grind this and apply Maakolam at the entrance and Krishnar paadam from the entrance till the Pooja hall. This small Paadam depicts the small steps of Sri Krishna and people trust Lord Krishna comes to each of their homes during the Pooja.
Nowadays, we get the small steps in stickers and people started buying them instead of Krishnar paadam depicted using the wet raw rice flour. However, the charm is drawing the small Paadam using the wet flour in white color. Some people dip their small kids legs in the wet rice flour and place the mark on the floor. This shows their level of enjoyment they have on this occasion.
Lot of people dress up their kids as Radha and Krishna as well. North India Celebrates this festival in a very grand manner.
Soak the raw rice in water for 2 hours and then drain the water. Grind in mixie into a smooth paste. Add few teaspoon of water if required while grinding. Using a small clean cloth draw the kolam.
Below is a small video of how to put the krishnar paadam using the wet raw rice flour.