There are just several key phrases in Japanese you would like to learn:

Hello, Good afternoon  = Kon-ni-shi-wa

Thank you         = Arigato

Welcome          = Yokoso (you unlikely need to speak it ;) but can listen)

Yes                  = Hai (very short and sharp – use your throat)

No                    = iie (like long ‘yea’, so please be careful with American “yes” pronounced in informal manner which can be taken for “NO”)

Good bye         = Sa-yo-na-ra

Good bye         = Ja-ne

(informal)

Something like «Otskare samateshta» (or Otsukaresama Tesuta =お疲れ様) – good bye between co-workers in one company.

Excuse me        = Su-mi-ma-sen

I’m sorry           = Go-men-na-sa-i (you can just say “So-ri” like ‘so-o-ree’)

 

Good morning   = Ohayo gozaimasu (there)

Good evening     = Konbanwa

Good night       = Oyasumi nasai

 

Where?             = Doko?

When?              = Itsu?

Why?                = Doshite?

How much?       = Ikura?

Who?                = Dare?

What?               = Nani?

Taken from own experience and Japanese phrase-book:

http://wikitravel.org/en/Japanese_phrasebook