Yet another break from my break:
At a dinner table, you are not supposed to let your elbows touch the table. At the bar, on the other hand, it is considered wise and appropriate. This may actually have to do with the now dying or dead custom of bringing your gun in to a saloon, and keeping your elbows on the table implies that you are not carrying such aggressively.
You are not supposed to open your mouth when chewing food, and are only supposed to use your hands when eating finger food. We Americans/Mainline Anglo-Europeans use forks and knives, although in some country's they will actually use tortilla like breads to grasp their food instead, especially Ethiopia. It was never much of a custom in Anglosphere nations to use a flattened bread, whereas fried foods that can be easily picked up (potato chips, chicken fingers...) filled the void of foods by hand, and cooking beef in larger pieces is also more common in English-speaking countries. Metalworking was also more common in these nations.
What conversation is allowable at the dinner table is regulated in the US to varying degrees dependent on region. This is unfortunate, as dinner is one of the main social gatherings of the day and restricted conversation lends easilly to superficiality. It softens people in mind, body, and soul. Makes them at ease as they dissolve in to the chair they are sitting in, slowly disappearing before their own decadence.
Of course, on the flip side, that only happens if you take it too far. Restriction in moderation makes for ease of relationship. And insisting on too much "real" may make new relationships more difficult to attain, crippling and restricting your life.
Maybe the best approach is to start easy and slowly remove the bounds. Build up. Give people their space at first and slowly approach. On the way, it's steady. Once you're there, it's fulfilling and enriching. Really, you can only make so many rules, relationships are an art. One basic rule though: It's about the other person.