Those customs and rituals or ‘Achaaraas’ that give positive and useful results are to be followed. But how to find the customs and rituals that are positive and useful is left to a person following the Sanatana Dharma (Hindu Dharma). Hindu scriptures like Dharma Shastras are peppered with hints which help in analyzing and practicing customs and rituals associated with Hindu religion.
The most important hint that the Dharma Shastras give is Sastram Pramanam – the first and the most important parameter a Hindu should consider before following a ritual is scientific results and original scriptures.
Next most important parameter is the advice of scholars and elders – Apta Vakyam Pramanam. This is bit a tricky because a person should develop skills to understand a true Guru from the showy and fraud ones.
The third parameter is direct experience – Pratyaksham Pramanam – this is something like you learn to walk after falling. We make mistakes but not repeating the same mistake sets us on the learning curve. Sometimes we get direct experience from various other sources and this can be used to gauge whether a particular ritual or custom is good for us.
Anumanam Pramanam – The fourth rule is guess work but this should only be applied when none of the above three parameters cannot be put to use.
In Hinduism, the individual is given the freedom to choose his/her path to reach the Supreme Soul. – Lord Krishna says to Arjuna in the final chapter of the Bhagavad Gita – Vimrusya Ethath Aseshena Yathaa Icchasi Thathaa Kuru: Hey Arjuna all that I have told you, critically analyze, and the option for accepting or rejecting is yours.
(Source - Inspired from a paper written on Customs and Rituals in Hindu Dharma Indian Institute of Scientific Heritage)