How to greet in Japanese

The Japanese Greetings.
The japanese people normally greet in every occasion of the day.In the morning they usually say 'Ohayo gozaimazu.The meaning of the term is 'good morning.Some of them use this term as only "Ohayo"to those who are considered as close friends or among  family members. Most often japanese people is bounded with the politeness of the words and also actions in each and every single occasion.Hence,if you forget to say "Ohayo gosaimazu it implies you are rude or impolite towards the other person.More often when working in a Japanese company its a very basic rule to great every companion with the term"Ohayo gozaimazu" in the morning.

              The morning period lasts until 12 p.m and then the afternoon begins.The japanese people use "konichiwa" for this period of time until the noon.This term "konichiwa is the meaning of good afternoon.Most of the japanese people however use this word as a greeting for all day.The reason is that it also implies the wish for a good day.So,they use "konichiwa in two meanings.Hence,Konichiwa can be used as a greeting of all day until mid night.At mid night the japanese people greet as "konbanwa"and it implies as good night.most of the japanese people use this term after six p.m in the evening.  

Apart from these three main greetings there are some other forms of greetings among Japanese people. most of them use the word "Omedetho" for any kind of greatings upon any knid of a special event occur in someones life.For example,""Otanjobi omedetho gosaimasu" means wish you a happy birth day.Then on the new year day japanese say "shinnen omedetho gosaimasu".It means wish you a happy new year.Then also upon the graduation of a student the japanese greet as "Sotsugiyo omedetho gosaimasu".The form of this word also changes in relation to the peoples relationships among them.If the relationship is very close they normally use it as "Omedetho".But among the higher status people most of the normal people wish them as Omedetho gozaimasu.The word gozaimasu is the honorific form of japanese word that aims to respect the person who is addressing.
When someone is departing or in a farewell Japanese people use the word "sayonara" and this means "good bye".This is normally used among all the Japanese people in every occasion or time of the day. However,the Japanese younger generation has now changed this word into English and they say "Bye Bye instead of "sayonara".However,its not a rule to use the typical word and everyone has their freedom to use whatever they like to use among their friends and the family.   
The simple greeting expressions in japanese
1.Ohayou gozaimasu-good morning
2.Konichiwa-good afternoon
3.Konbanwa-Good night
4.Sayonara-good bye
5.Omedetho gozaimasu-congradulations.