Greetings

おはよう（ございます）。		Ohayoo (gozaimasu)	Good morning (polite)
こんいちは。		Konnichiwa	Good afternoon
こんばんは。		Konbanwa	Good evening
おやすみなさい。		Oyasuminasai	Good night
いいゆめ。	Iiyome		Good night
‘Konnichiwa’ is generally used for day time.
さようなら。		sayoonara	Good bye
じゃね。		jane	Good bye
それじゃ、また。		soreja mata	Good bye
People usually say ‘sayoonara’ if they are going to leave for a long time. The other two are more common to use.‘soreja mata raishu' is what I say to my Japanese teacher when I leave the class. It means‘see you next week'.
ありがとう（ございます）。		Arigatoo (gozaimasu)	Thank you (polite)
すみません		Sumimasen	Excuse me/sorry
ごめえ		Gomee	sorry
いってきます。		Ittekimasu	I’ll go and come back
いってらっしゃい。		Itterasshai	Please go and come back
ただいま。		Tadaima	I’m home
おかえりなさい。		Okaerinasai	Welcome home
For example, when I leave my home, I would say ‘ittekimasu’ to my mom. And my mom would say ‘itterasshai’ to me. It just like I say "I'm going out", and my mom says "take care". When I come back home, I would say ‘tadaima’ to my mom. And my mom would say ‘okaerinasai’ to me. Well, I live by myself now, so I don't have anyone to say with. But it's good to practice whenever I go out and come back. (I hope it's not that stupid @.@)
いただきます。		Itadakimasu	Thank you for the meal (before)
ごちそうさま。		Gochisoosama	Thank you for the meal (after)
はじめまして。 どうぞ　よろしく。		Hajimemashite Doozo yoroshiku	How do you do? Nice to meet you
When people introduce themselves, they usually say ‘hajimemashite. Doozoyoroshiku’ at the end. It means something like "It's the first time we meet each other, please tell me if I did something wrong."