The short answer
Homa is a structured act of worship, not simply “burning offerings.” The devata, mantras, substances offered and ritual sequence depend on the purpose of the ceremony.
Why there are many Homams
Ganapati Homam, Rudra Homam, Navagraha Homam, Ayushya Homam, Chandi Homam and other forms are not interchangeable labels. Each has its own devotional focus and traditional structure.
What families should prepare
The most important preparation is to confirm the exact Homa, venue, fire-safety conditions and priest-provided samagri list. Generic online lists often contain unnecessary quantities or items that belong to a different tradition.
What happens during the ceremony
The priest establishes the ritual context, performs the required worship and guides the offerings. Family members are invited to participate at appropriate moments.
Traditional purpose, not a guarantee
A Homa is an act of prayer and devotion. It should be described in terms of what the family traditionally prays for, never as a guaranteed cure, financial result or magical transaction.
This page explains family-facing principles. Exact practice can differ by sampradaya, Vedic tradition, region and family custom. Shri Venugopal Shastry can clarify what applies to your ceremony.