In the Tamil culture-
- Traditionally, we eat our food using our hand. Therefore, do not ask for spoons and forks while eating with a Tamil family. It is as odd a thing to do, as eating French food by hand without using cutlery.
- Use only one hand (usually the right one) to eat. The other hand should not touch the plate (don't even keep it on the table). This hand can be used for re-serving yourself from the main bowls.
- Do not touch the serving spoon of the main bowl, with the hand you use for eating. This is called 'echhil kai' (Tamil words) literally meaning 'Saliva hand'. It indicates the hand you use to eat. It is believed that contaminating food by touching things with your saliva hand makes the food impure. It is only to avoid spreading any kind of infection or disease from one person to other.
- Do not touch other people's plates while eating (not even with the unused hand). Again, 'echhil kai'.
- In some homes, people prefer sitting on the floor to eat.
- Do not get up in the middle of a meal. It is considered rude and disrespectful of food and the people you are eating with.
- DO NOT WASTE FOOD. Again, it is considered as rude and disrespectful. If you are unsure of the quantity of food you want to eat, serve yourself small portions and go for a re-fill. It is completely okay if you end up serving yourself thrice, but wasting food is out of question.
- Never lick your plate directly with your tongue.
- Never lick the main bowl. Even if the dish is over, and you want to scrape the dish clear of any morsels, use a spoon to get it out.
https://www.quora.com/What-are-the-traditional-dining-etiquette-of-South-Indians?srid=nDWJ
