What you actually need on a trip is narrow: get someone’s attention, ask where something is, ask what it costs, and say you did not understand. These four things cover most of a week in Japan.
Coloured text marks the part that matters: usually the word to swap for your own, sometimes the small word doing the work.
The four you use hourly
すみません。
Sumimasen.
Excuse me. / Sorry. / Thank you.
Does all three jobs. If you learn one word on this sheet, learn this one.
ありがとうございます。
Arigatou gozaimasu.
Thank you.
お願いします。
Onegaishimasu.
Please. / Yes please, go ahead.
Attach to anything you are requesting, or use alone to accept an offer.
大丈夫です。
Daijoubu desu.
I am fine. / No thanks.
Means both. At a till it reads as declining, which is usually what you want.
Getting around
駅はどこですか。
Eki wa doko desu ka.
Where is the station?
Swap 駅 for any place. This one frame handles all "where is" questions.
この電車は渋谷に行きますか。
Kono densha wa Shibuya ni ikimasu ka.
Does this train go to Shibuya?
何番線ですか。
Nan-bansen desu ka.
Which platform?
ここまでお願いします。
Koko made onegaishimasu.
To here, please.
In a taxi, while pointing at a map or an address. Solves the pronunciation problem entirely.
歩いてどのくらいですか。
Aruite dono kurai desu ka.
How long is it on foot?
Shopping and paying
いくらですか。
Ikura desu ka.
How much is it?
これをください。
Kore o kudasai.
This one, please.
Point and say it. Works for absolutely everything.
カードで払えますか。
Kaado de haraemasu ka.
Can I pay by card?
袋はいりません。
Fukuro wa irimasen.
I do not need a bag.
見ているだけです。
Mite iru dake desu.
I am just looking.
At the hotel
予約しています。
Yoyaku shite imasu.
I have a reservation.
チェックインお願いします。
Chekku-in onegaishimasu.
Check-in, please.
荷物を預かってもらえますか。
Nimotsu o azukatte moraemasu ka.
Could you hold my luggage?
Standard before check-in or after check-out.
Wi-Fiのパスワードを教えてください。
Wi-Fi no pasuwaado o oshiete kudasai.
Could you tell me the Wi-Fi password?
When you are stuck
わかりません。
Wakarimasen.
I do not understand.
もう一度お願いします。
Mou ichido onegaishimasu.
One more time, please.
ゆっくり話してください。
Yukkuri hanashite kudasai.
Please speak slowly.
英語が話せる人はいますか。
Eigo ga hanaseru hito wa imasu ka.
Is there someone who speaks English?
道に迷いました。
Michi ni mayoimashita.
I am lost.
助けてください。
Tasukete kudasai.
Please help me.
Genuine emergencies. For everyday trouble, すみません plus your problem is enough.
Worth knowing
これ plus pointing beats vocabulary
これをください and これは何ですか cover any object you cannot name. You do not need the word for the thing.
ください vs お願いします
ください asks for a thing you can hold. お願いします asks for a service or an action. At a taxi it is お願いします, at a shop counter it is ください.
Say すみません before the question
Opening with it is what makes a stranger stop and listen. Launching straight into your question reads as abrupt.
One-line rule: すみません to open, これ plus pointing for anything you cannot name, どこですか and いくらですか for the two questions you will ask most, わかりません when it falls apart.