Offer a namaste (palms together, slight bow of the head) as your default greeting, particularly with older people or in situations where you’re unsure whether a handshake would be welcome. Let the other person initiate a handshake if they want one.
In some families, younger members bend to briefly touch an elder’s feet with both hands, then touch their own hands to their forehead, when greeting them at home or during festivals. The elder responds by placing a hand on their head and offering a blessing (ashirwad). This is a family/regional custom rather than something expected of guests or strangers.
Both gestures go by different names depending on region: namaste itself becomes namaskar, namaskaram, or nomoskar in different parts of the country, and the feet-touching greeting is called dhok deun or page lagun in Rajasthan and Uttar Pradesh, and pairin pona in Punjab.