Sake is served in tokkuri (small sake bottles) and poured into o-choko (small sake cups). It is polite to pour sake into each other's cup when you are drinking with someone. It's good to know whether your company's cup is empty or not. When someone wants to pour you more sake, you should hold your o-choko cup up.
Sake can be served hot or cold. Hot sake is called atsukan, and cold sake is called hiyazake. Winter is the best time to enjoy hot sake.
Legal drinking age in Japan is 20 years old. To drink sake, it's a good idea to go to izakaya, which are Japanese-style bars. Izakaya serve various dishes which come in small portions, and they are usually reasonably priced. The atmosphere of izakaya is casual. Try to visit an izakaya and have fun when you go to Japan.