A: The usual misconception is that sitting at the counter automatically proves more costly than sitting at a table or on a tatami floor. The price will vary accordingly to what you have ered wherever you sit. The fact that customers sitting at tables usually order "sushi sets" will tend to demonstrate that it is cheaper, but you can order the same at the counter. On the other hand, sitting at the counter will entice you to order sushi piece by piece and venture into some exotic requests, hence a higher price. I myself always sit at the counter because I can enjoy the vital opportunity to converse with the chef, watch his technique and have a good look at the available ingredients of the day. 

A:Yes, for two reasons: 
First, the carefully-made "nigiri zushi" will somehow collapse on itself after some time and will not look so appetizing. 
Second, the "neta" will dry up and will lose some flavour, tenderness and freshness. That is why I have always strongly felt gainst the very popular "kaiten sushi" (conveyor belt) restaurants! 
The trick is to order one "nigiri zushi" after the other and savour them individually, one more reason to choose a counter seat. 

A: As rice is actually the most important part, only high-quality rice such as "Akita Komachi" should be used. 
Next, the balance between the rice vinegar, sugar and salt is very important. Too much of any ingredient will leave an overwhelming taste inside the mouth to the detriment of the other ingredients. Not enough salt will also be detrimental. Only experience will dictate the right amounts! 

A: Do as you like! 
I myself very often ask the chef to add soy sauce directly onto the sushi!

A: It should be. If the "gunkan" (literally "mother ship", term taken from the Navy) is properly made! A "gunkan"-style "nigiri zushi" is made with a strip of dry seaweed wrapping the rice ball leaving the top free and securing the topping ("neta"). moreover I would ask the chef to season it with soy sauce to avoid dropping it into my soy saucer saucer (sorry for the pun!) 

A: That is another misconception. Long ago, sushi "neta" were exclusively made of boiled, pickled or salted fish. 
As hygiene, refrigeration and preservation have greatly improved, we have access to better and better fresh fish. But in some cases, such as for "maguro" (tuna), it is best to leave the fish rest in a secure place for a while before eating it. 
"Maguro" is at its best after a week left in a cold (not frozen) place. 

A: Well. that probably depends both on the chef's and the customer's preferences. With a different cut or presentation, various parts of the fish will offer a different exposure to the eater's palate with consequent different tastes and flavours. 

A: No. This is being dictated by two factors: 
a) Easy-to-hold or to-eat portions. 
b) Sometimes when the "maki" is shared so smaller portions (6) will be more practical and pleasing to the eye. 

A: A male fish, because a female loses part of its own nutrients for egg (roe) production, especially in the case of salmon and white-fleshed fish. 

Robert-Gilles Martineau