There are many ways to greet someone in Indian. The handshake used in Western culture is not one of the accepted forms when greeting anyone on the street. The greeting that replaces it is the “namaste” - both hands together and giving a slight bow. That’s respectful when meeting anyone. A handshake is acceptable between two men, but never between a man and a woman.
To greet elders, the most often used sign of respect is touching their feet. Since I was not raised with this tradition, I will not try to explain how it’s done. However, there are videos and instructions for this particular greeting online since it is one of the most widely used signs of respect and greeting by Indian Hindus when greeting an elder.