Homahuti is decided based on Agni Chakra. The Chakra should be used while doing Havan for Griha Pravesh, Graha Shanti i.e. pacification of planets, conquering enemy, etc. The result of Homahuti depends based on Ahuti of Graha.
Homahuti is not considered while performing Yagya for Vivaha, Upanayana, Mundan i.e. tonsure ceremony, Puja done for Lord Vishnu, Goddess Durga during Navaratri, during Eclipse, propitiation of planets during transit, Puja of family deity etc.