In Japan, people greet each other by bowing.
A bow can ranges from a small nod of the head to a deep bend at the waist. A deeper, longer bow indicates respect and conversely a small nod with the head is casual and informal. If the greeting takes place on tatami floor, people get on their knees to bow. Bowing is also used to thank, apologize, make a request or ask someone a favor. Bowing with your palms together at chest level, as done in Thailand, is not customary in Japan.
Most Japanese do not expect foreigners to know proper bowing rules, and a nod of the head is usually sufficient. Shaking hands is uncommon, but exceptions are made, especially in international business situations.
At formal meetings, business cards are exchanged during the introductions.
At shops and restaurants, customers are typically welcomed by the staff with the greeting "Irasshaimase". No response from the customer is required, and a smile and a nod with the head would suffice for those who want to reciprocate the greeting.