Drinking
Do not start drinking until everybody at the table has a drink and the glasses are raised for a drinking salute, which usually is "kampai".
When drinking alcoholic beverages, it is customary to serve each other, rather than pour your own drink. Periodically check your friends' cups and refill their drinks if their cups are getting empty. Likewise, if someone wants to serve you more alcohol, you should drink some from your glass before holding it towards that person.
While it is considered bad manners to become obviously drunk in some formal restaurants, for example high-end restaurants that serve kaiseki ryori (Japanese haute cuisine), the same is not true for other types of restaurants such as izakaya, as long as you do not bother other guests.
If you do not drink alcohol, it is not impolite to say so and request for other beverages instead. Non-alcoholic beverages that are usually available include alcohol-free beer, tea, juices and carbonated drinks.