Question: I am catholic and I want to pratice the Hindu faith, is there any special ceremony I have to perform to become Hindu?
There is no external ritual one must perform to convert to Hinduism. To be a Hindu only requires one to apply the philosophical teachings of the scriptures such as Bhagavad Gita in one’s daily life. The word dharma (religion) actually refers to that which cannot be separated from an object. For example heat cannot be separated from fire. In the case of the soul, the quality of servitude cannot be separated from it. Everyone is ultimately a servant. When we understand this and engage in service to the supreme, we are factually practicing our inherent dharma. Rituals have no bearing on our inner nature. They only pertain to the external body. One day this body will die, and the rituals will disappear, having no connection to our soul. The goal of life is to revive our inherent and eternal dharma. What ever is favourable for that should be accepted, and whatever is unfavourable for that should be rejected.
You must try to understand what is your path to God, and cultivate that process of service, either through devotion (bhakti), knowledge (jnana), or activities (karma). If you are sincerely endeavoring on your path you are a Hindu. There is no external ritual needed to confirm this. Those who put more importance on the external rituals have themselves failed to see the soul in the heart of all living entities. They are unfortunately seeing the external body as the self.