Here are some of the extremely basic Japanese phrases that I think everyone should learn! Dictionary meanings are all taken from Jisho.org!

よろしくお願いします (Yoroshiku onegaishimasu) – Please remember me; please help me; please treat me well; I look forward to working with you.
I have been translating this as ‘we ask for your favor’ as well. It’s a greeting/expression that you hear a lot, a lot. Maybe it’s just me, but I think ‘we ask for your favor’ sounds so much more awkward in English. I guess it’s because we don’t greet people that way in English? But this phrase is on the top of my list on words that I wish to leave in Japanese.

Broken down, お願いします (onegaishimasu) just means please. It is used alone a lot. To mean things like ‘please stop it’, or ‘please be serious’, or just ‘please help us/treat us well’ etc etc. Like when someone screws up in VSA, and Nino goes ‘onegaishimasu!’, he’s trying to tell that person to please stop messing up/fooling around etc… I think you can get the idea.

よろしく (宜しく, yoroshiku) on it’s own has several meanings. I quote from my favorite website:
1. Well; properly; suitably.
2. Best regards; please remember me; please treat me favorably (favourably); please take care of.
3. Just like…; as though one were…
4. By all means; of course. (as よろしく…べし)

For this phrase… I’ve pretty much only seen it used as no. 2. Basically the same way as yoroshiku onegaishimasu.

ありがとうございます (arigatou gozaimasu) or just ありがとう (arigatou). Aw come on, you know this one right? It just means thanks, or thank you. It’s a very straight forward meaning.

おはようございます (ohayou gozaimasu) or just おはよう (ohayou) – good morning. (Pronunciation wise it’s o-ha-yo. But the “yo” is a long sound, hence the u at the back)

こんにちは (今日は, konnichiwa) – Hello; good day (daytime greeting)
The kanji literally means ‘today is’. It used to be that they would greet each other by say ‘Today is a good day’ or something, but as language go, they evolve with usage, and eventually it was just shortened to ‘today is’.

こんばんは (今晩は, konbanwa) – Good evening
Again, like konnichiwa, it literally means ‘tonight is’.

お休みなさい (oyasuminasai) – Good night

Now, you may have noticed. What does ございます (gozaimasu) mean? Well that phrase actually can be written in kanji! It goes like this: 御座います – To be; to exist.
It’s used in the polite form, so saying ohayou gozaimasu is more polite and formal than just saying ohayou.

いただきます (itadakimasu) – Expression of gratitude before meals.
Ah this! Another phrase with no English equivalent! Nor a proper Chinese equivalent either.

ごちそうさまでした (gochisousama deshita) – That was a delicious meal (said after meals); what a wonderful meal.
Gochisou literally means a feast, or a treat.

ただいま (tadaima) – I’m home
Used as an expression to announce your arrival at home. We know that Jun says this when he arrives home too. Even though he stays alone. He says he wants to practice for marriage life or something hahaha. He says oyasuminasai to himself too.
Well besides being used as a greeting, this phrase can also mean “Presently; right away; right now; just now”.

おかえりなさい (okaerinasai) – Welcome home
Used as a greeting to welcome someone home. So the person who just returned will say ‘tadaima’, and the one at home would say ‘okaerinasai’ or ‘okaeri’ for short.
And since we are talking about Okaeri, as you know Arashi has a song with that title. Besides being a short form for Okaerinasai, it also means ‘return’.

失礼します (shitsurei shimasu) – Excuse me
Well 失礼 (shitsurei) literally means you ‘lost manners’, i.e. impolite. As an expression it literally means ‘I’m going to be rude’. It’s generally used to mean ‘excuse me for disturbing’ or ‘excuse me for the intrusion’. This is being said when you enter rooms.

おじゃまします (お邪魔します, ojyama shimasu) – Excuse me for disturbing (interrupting) you; greeting used when entering someone’s home.
邪魔 (jyama) means ‘Hindrance; obstacle; nuisance.’ So similar to the earlier phrase it literally means ‘I’m going to be a hindrance’.

済みません (すみません, sumimasen)
1. excuse me; pardon me; I’m sorry
2. thank you

Ok, you’d hardly see this word written in kanji… But it’s good to know anyway, right?

So you’re probably wondering what’s the difference between すみません and 失礼します. Shitsure shimasu is used when you’re going to do something rude. Like entering a room (you’re disturbing the people inside!) or picking up a phone call during a meal. Sumimasen means more like a subtle, less apologetic sorry. Like “Sorry, could I ask a question/disturb you for a minute”, or “Sorry, could you please let me through?” Note that it’s not the “I did something bad/wrong and need to apologise sorry,” in which case gomenasai should be used.

いらっしゃいませ (irassaimase) – Welcome (in shops, etc.).
If you go to a Japanese restaurant, you’d hear this phrase spoken in its various levels of accuracy a lot. Well at least that’s the case in my country…

おつかれさま (otsukaresama) – 1. Thank you; many thanks; much appreciated. 2. That’s enough for today.

頑張って (ganbatte) – Hold on; go for it; keep at it.
Well I’m sure we all know this phrase too! It’s hard to get a good English equivalent too, although the concept itself is easy enough to understand. I would translate it as ‘do your best’ (of course, it varies with the context too) as compared to the meanings the website gives me.