The most common greetings in Japanese are "konnichiwa," meaning "hi" and "good afternoon," and "konbanwa," meaning "good evening." For informal situations, "ohayo" is an appropriate word for "good morning," and "ohayo gozaimasu" is reserved for formal interactions with superiors, such as a boss.
The informal way to ask people how they are is "hajimemashite" or the formal "o-genki desu ka." When taking leave of superiors, one says "shitsurei shimasu." The literal translation approximates as, "I will be rude," but the intent is to excuse oneself with extreme politeness and to apologize for leaving the person. Common departure pleasantries include "mata ashita," meaning "see you tomorrow," and "say?nara," or "goodbye."
In addition to the relevant vocabulary, bowing is an extremely important component of greetings in Japanese culture. When addressing someone in informal situations or when the persons involved are equals, a slight nod of the head suffices for the bow; however, in circumstances where more formal or respectful decorum is expected, the bow is usually deeper and longer, creating a near 90-degree bend at the waist. Most Japanese people do not expect foreigners to be completely versed in bowing protocol, so they customarily accept the aforementioned nod of the head or a Western-style handshake. Another important element of any greeting offered to a Japanese person is the spirit and energy with which it is given. Japanese culture places special emphasis on honoring people during interactions; thus greetings that appear lazy, half-hearted or offhand are likely to be insulting.