In Japanese, there are a lot of set expressions that are used in various situations. When you arrive at your house, you say one thing yet when you enter someone else’s home, you say something else. Other situations include when you start and finish eating or when you’re leaving your house. I remember when I was learning Japanese, I wished that I had a handy list of such expressions. (I looked on google and couldn’t find such a list) So as a service to the Internet community, I’ll post such a list here.

Eating
Because I’m such a fan of eating, we’ll first discuss the expressions used before and after you eat.

１．いただきます
– Said before a meal. Literally means, “I will receive” using the humble form of the verb “to receive”.
２．ごちそうさまでした／ごちそうさま
– Said after a meal. Literally means, “It was a feast”. 「ごちそうさま」 is a less formal version.

Greetings
You really ought to know these already if you’ve spend any time studying Japanese.

１．おはようございます／おはよう
– Good Morning.
2.　こんにちは （The 「は」 is pronounced 「わ」）
– Good Day.
３.　こんばんは （The 「は」 is pronounced 「わ」）
– Good Evening.

Expressions for coming and going
Here are some more expressions to use when you are coming or going, usually from home.

１．行ってきます
– You say this when you go out. Literally it means, “I’ll go and then come.”
2.　いってらっしゃい
– You say this to the person leaving if you are staying behind.
３.　ただいま
– Used when you come back home.
４.　お帰り／お帰りなさい
– Welcome back. お帰り is a less formal version

Work-related
Here are two more expressions for work-related occasion.

１．お疲れ／お疲れ様／お疲れ様です
– Most often used as a parting expression after work. If the person is leaving, you can also say the past tense: お疲れ様でした. お疲れさん is also a possibility though mostly only used by middle-aged men.
2.　ご苦労様／ご苦労様です
– This expression is used when somebody has finished doing some work for you. Be careful with this one because it puts you in a higher position of having requested the work. You can also say ご苦労さん though again, this is used mostly by middle-aged men.

Other expressions
Here’s some more that I couldn’t fit into it’s own category.

１．お休み／お休みなさい
– Good night. お休み is a less formal version.
2.　お邪魔します
– When you enter somebody else’s home. Literally means, “I will intrude”.
3.　失礼します
– Polite way to indicate you are leaving. Also used before hanging up on the phone. Literally means, “I’m doing a discourtesy.