Question: how to do amavasya vrat?
Answer: Offer water to Sun and Tulsi in the morning reciting Gayatri mantra for 108 times.
Offer water on the Shivling.
Offer rice to a cow.
Place Tulsi at a peepal tree. ... 
Offer home made Puri, Kheer and vegetable to ancestors and then consume same.
Donate clothing, food and sweets to poor.