Sri Krishna Janmashtami or Sri Krishna Jayanti is mainly celebrated in Bhagavan Krishna or Vishnu temples. You can also perform special pujas and rituals at home. Here is a guide to Sri Krishna Janmashtami puja procedure in Hindi. The how to do guide of Sri Krishna Jayanti pooja is provided by Kamakoti mutt.
Link – Hindi Sri Krishna Janmashtami Puja pdf
The puja is performed mainly for peace and prosperity. It is also performed for health of children in the family. Married couples perform it for having safe child birth.
The rituals associated with the puja are based on shastras followed by a particular tradition. It might not be applicable in all regions.