You will find here some tips when eating in a restaurant in France. We'll be covering other countries soon, as every place has its own rules and practices. If you have specific countries you would like us to cover, let us know!
Drinking soda in any restaurant that has a minimum of standing usually makes the French cringe. And rightly so. French cooking doesn't have fatty food that absorbs the acidic impact of most sodas. The stark taste usually numbs the taste buds and anything subtle will go by unnoticed. In addition, one of the fundamentals of French cuisine is separating sweet from salty. Finally, a red flashy can just looks terrible on a table, especially when beside a nice bottle of wine or even sparkling water.
Don't expect the waiter to barge in every 5mn checking if everything is OK. In France, you don't tip, so the waiter isn't pouring all over you a big fake smile to make sure he gets a big 15! If you need something, lift you hand, don't yell, don't snap, a gentle wave and a smile should suffice.
Paws on Table
Though perfectly normal in many countries, leaving one arm on the lap is a big no-no in baguette country. You need to keep both hands on the table. Leaving one hand astray makes the locals wonder what exactly you are doing, or more sympathetically, just gives them a perception of laziness.
The soul of the "table" is precisely its ephemeral nature. Taking a picture is like emptying the moment of its spirit. A gastronomical meal is a form of spiritual awareness seeking Zazen or ultimate consciousness. To keep a souvenir, writing is strongly recommended, notably because that implies an effort.
Licking your wounds
This shouldn't even be necessary, but unfortunately, yes, it is. One does not lick a knife in a restaurant. It's either a parvenu thing or some odd way of licking some emotional wound. It's a total lack of class.
With some exceptions, the waiter always uncorks in front of you. If he brings the bottle already uncorked, send it back. This is because of the dubious practice of putting cheap wine in a bottle with a nice label. And since many won't be able to make a clear difference, it's a big margin for the restaurant and piquette for you.