India is quite conservative in dressing, especially for women. This country is not suitable for open shoulders or shorts unless you are on a beach or in South Mumbai. Try to wear clothes at least of knee length and keep your shoulders covered.
If you are a vegetarian, you are going to love India.
They have many varieties of tasty food options for you and it’s always marked with a green dot that makes shopping easier. In an opposite case, take into consideration that some people are not comfortable eating food in the same room with non-vegetarian products. This is related to stays in some AirBnb or Guest house type of spaces.
Indian culture teaches respect towards elderly people for their experience and knowledge.
If you are invited to a traditional Indian function, no one will expect you touching feet to show respect as it’s accustomed in India. However, ignoring elders even if you are not acquainted might be perceived as a rude behavior sometimes. A formal “Namaste” greeting will do in most of the cases.
In India there are certain places where only women are allowed and vice versa. It’s applicable for transport, some religious places, some queues, trial rooms, etc.
Pay attention to this, because in some cases you can be punished: e.g. if you are a man staying in a women train car in Delhi metro you can be scolded and fined.
India is a conservative country that has some reservations about showing emotions in public. It’s mostly about couples. Don’t mix it up with friendship. You will see girls hugging girls while greeting if they are close friends or guys hugging guys, but girls hugging guys is not allowed in many places. In some Indian states, you can be fined and even arrested for showing public affection towards the opposite gender. Try to keep your emotions with you.
Always take off your shoes before you enter any temple and dress conservatively.
There are some temples that don’t allow non-Hindu, some are only for men, and others have specific rules for visitors. I would advise researching about a temple you plan to visit if it’s not a known tourist attraction.