Basic Japanese Greetings

Ohayoo - Good morning (casual).
You can use this in the morning before noon. For polite form, you can use "Oha yo gozaimasu". If you find pronounce difficult, first you can say, "Ohio" instead. Then, try "Oha yo". Yeah. I hope this should help you.

Ohayoo Gozaimasu - Good morning (polite).

Konnichiwa - Good afternoon, Hello.
You can use around noon, Please do NOT say "Koni-chiwa". When you speak Japanese, please try NOT to connect two words. "Kon nichiwa" means "Hello", but this is NOT "Hello" in the telephone conversation.

Konbanwa - Good evening.

Sayoonara - Good-bye.
For casual form(especially used among young people), you can use "Ja-ne". [This is not "Jane"(laugh)] Or "Bai bai"(Bye bye).

Oyasuminasai - Good night.

Arigatoo - Thank you.

Arigatoo Gozaimasu -Thank you (polite).
For the polite form, you can use "Doumo-ari-gatou" or "Dou-mo-ari-gatou-gozaimasu" (more polite even).

Sumimasen - Excuse me, I'm sorry.

Iie - No.; Not at all.

Itterasshai - Please go and come back.
This is very Japanese. In fact, I cannot give you a translation for this greeting. You can say this to someone in your family when he or she leaves the house. Japanese people say this to express their hope that family members will come back to the house safely.

Ittekimasu - I'll go and come back.
This is the reply to the previous greeting, "Itte rasshai". When someone in your family says "Itte rasshai" to you, you respond, "Itte kimasu".

Tadaima - I'm home.

Okaerinasai (Oka-eri) - Welcome home.
-This is the reply to the previous greeting, "Tadaima". For the polite form, you can use "Oka-eri-nasai".

Itadakimasu - Thank you for the meal. (Before eating).
Japanese people say "Ita-daki-masu" before they start to eat, its a form of appreciation for the people that made that made the food (mother, cook), the farmers or gods responsible for the food.

Gochisoosama - Thank you for the meal. (After eating).
Japanese people say "Gochisou-sama-deshita" after they finish eating. 

Hajimemashite - How do you do?
(This has many meanings, but should be said only when you first meet someone).

Doozo Yoroshiku - Nice to meet you.
(Said on first meeting also).

There you go ^-^