Saying “hello” seems to be the simplest thing
Unless your interlocutor takes the initiative, never shake hands, it is considered to be impolite, like an impure act. Greet people saying “Namaste” joining your two hands in front of your chest. It is the equivalent to “Hello” in Europe.
Kissing each other is not done in public, it is considered as very disrespectful and impolite.
The modest side of Indian couples will surprise you. They never kiss in public nor do they show each other any sign of affection. So keep you marks of affection discrete. You can only touch your wife!
On the street, a man can touch another man but never a woman.
A woman can touch another woman but not a man.
A man does not speak to a woman if she is alone. If she is accompanied, it is allowed.
A woman does not speak to a man if she is alone. If she is accompanied, it is allowed.
In a restaurant :
If you eat in a restaurant with Indian friends, do not be offended if one of them gets up and goes to eat at another table when the food is served (some vegetarians are not allowed to eat and share a table with a non-vegetarian… because of their religious doctrine)
In India, people eat with their fingers, only those of the right hand, the left hand is considered to be impure.
In a family :
If a family invites you, you can give them some sweets, cakes etc.… above all don’t offer your help, it is considered to be ungracious.
Even if the meal is delicious, which it will be; avoid drowning them with compliments on the meal.
Don’t say the children are good-looking; our Indian friends think that it brings the evil eye.
On the train :
If a person is asleep lying in the corridor, it is better to wake him up than to step over him, it is a sign of respect.
On the bus :
Normally a man does not sit next to a woman, the contrary is also true, except if you are married.