Up at Japundit there is a question about what is the vital vocabulary needed when visiting Japan. My answer is based on my belief that you should keep it simple. Hence the lessons are limited to very simple words/phases. Note that this is NOT going to make you fluent in Japanese, indeed it will cause you to mispronounce things slightly, nor will it necessarily be polite but it will get the point across.
The number one most useful phase in Japanese is this one
Onegai shimasu (pronounced mnemonically as Annie Guy She Mass)
which means "please (give me/take me to/connect me to/do this for me) ....". You state the person, action, object or destination you want then say "onegai shimasu" and your wish will be performed by the person you are talking to. Examples:
if you want to call an office and talk to Mr (or Ms) Suzuki, then when the phone is answered you say "Suzuki-san onegai shimasu".
if you want a taxidriver to take you to the "Tokyo Prince Hotel" then when you get in the taxi you say "Tokyo Prince Hotel onegai shimasu" (you would get additional bonus points if you remembered to pronounce Hotel as Hoteru)
if you wanted to buy the thing you are pointing at (food, present, ...) just say "kore onegai shimasu" (Kore is mispronounced korrie and means this)
The most useful words to go with onegai shimasu are
Beeru (bee rue) - Beer
Osake (oh sackey) - Sake
Akawain (acka wine) - Red wine
Shirowain (she row wine) - White wine
And when sobering up
Mizu (me zoo) water
Kohii (kor he) coffee
When answering questions (or listening to the answer):
hai (hi) - yes
ie (ee ye) - no
If you want to say something more complicated than your limited Japanese will permit then you probably want these phrases:
Eego dekimasuka? (Eh go deck ee mass ka?) - do you speak English?
Yukkuri kudasi (you coo ree could a sigh) slowly please
Go to any bar and the following phrases will help with "beeru onegai shimase" when you (want to) make some friends
Sumimasen (see ma sen) - Excuse me (good for attracting attention)
Arigato (A Ri[n]g A Toe) - Thank you
Doh-itashi-mashite (don't touch my moustache) - you're welcome
Kampai (Cam Pie) - Cheers
Also in the unfortunate occasion that some new drinking buddy is offering to buy you a beer but you must decline because you actually have to appear sober at work tomorrow there is this word
iranai ([h]e ran eye) - I don't need/want it
this isn't the most polite way of saying it but hey you and your buddy are half plastered at this point so you won't remember anything longer and he (she) will forgive you. It can also be used in other circumstances where someoone is offering something that you don't need from a blow-job to a piece of blow-fish . Also "mo" means more in quite a few cases so
fugu iranai (foogoo e ran eye) - I don't want any blowfish
mo iranai (moe e ran aye) - I don't want any more
beeru mo onegai shimasu - more beer please [gramatical pedants: yeah I know its not 100% right]