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