Dining etiquette is different in every country. If you travel often, this infographic published by 'The Restaurant Choice' will be extremely insightful.
The infographic is a visual representation of meals from different countries. To represent Italy, a plate of pizza is depicted; it's disrespectful to ask for extra cheese on your pizza and to only tip 5-10% for exceptional service because gratuity is already included on the bill.
While some etiquette is universal and presumable, many countries have surprising rules when dining! In France it is a faux-pas to split the bill, in China belching serves as a compliment to the chef and in India it is deemed dirty to eat with your left hand. The most surprising of all is Japan's dining customs; they believe tipping staff is very rude and think the louder you slurp your soup the better!